Antiallergic: does it give you sleep? See how it works, when to use it and the price

It is not difficult to find someone who has an allergy – about 2 billion people worldwide suffer from allergic complications, according to the American Academy of Allergy and Immunology. Many people have exaggerated immune responses.

Although common – and therefore sometimes underestimated – they can be quite dangerous, causing suffocation and respiratory arrest.

So many people are affected that some experts suggest considering allergies in general as an epidemic.

It may even sound exaggerated or strange to think about allergy epidemics, but the data indicate that there are currently around 25 million Brazilians with some type of allergy – an index 50% higher than 20 years ago.

In the midst of this increase, the consumption of medicines to stop allergic crises has also increased. On average, the sale of antihistamines – which are the drugs that fight allergies – generates something close to 8 billion dollars a year.

Although it does not definitively solve the problem, an antiallergic can be very functional after an insect bite or contact with an irritating substance.

Do you know what happens in your body after taking an antiallergic medication


What are antiallergic?

Antiallergics, also called antihistamines , are medications that act by controlling allergy symptoms, such as redness of the skin, itching, shortness of breath and choking.

The basic mechanism of action of antiallergic agents is through the inhibition of histamine – a substance released in excess when the organism comes into contact with the allergenic agent.

Although it is difficult to determine exactly the origin of allergies, which can be due to genetic, environmental or behavioral inheritance (or all together) – it is known that many antiallergic drugs can work for different types of reactions.

This is because, in most cases, it does not matter exactly which irritating agent – it could be pollen, strawberries or a chemical product – the body’s response will be more or less similar.

But it is worth remembering that the biological response is similar, but the symptoms may vary according to the person and the amount of exposure to the allergenic agent.

For example, it is possible that 2 people are allergic to the same perfume. One of them may sneeze and have an affected airway, while another has red patches on the skin and rashes.

In such cases, both can take the same medicine – or not. This is because even though the substance is the same, the level of sensitivity and the reaction of the organism can be different, making one need higher dosages or a stronger medication.

However, both need a remedy that inhibits histamine action and relieves symptoms. That is, it is time to resort to antiallergic.

Currently, two types of antiallergic agents are commercialized: the 1st generation – called sedatives, which are older and, in general, have more side effects – and the 2nd generation – called non-sedatives, which are younger and with less adverse effects.

According to ANVISA, pharmacies do not need to retain the antihistamine prescription, however, it is important to reinforce that a medical prescription or pharmaceutical guidance is required for purchase .

What are allergies?

In practice, almost everyone knows what an allergy is. Itchy skin, redness, rashes similar to insect bites and swelling. Sometimes they are quickly associated with the cause – a perfume or a food -, other times the cause is not well known. Those are allergies.

But the biological mechanism is much more complex and still generates uncertainties in the medical environment. This is because it is not clear why some people are extremely sensitive to a small amount of blackberries or dust, for example.

What is known is that there are genetic and environmental factors involved in the development of allergies. There is about a 40% chance that a child will be allergic if a parent is also allergic.

However, for sneeze or itch attacks to occur, it is necessary to participate in the environment or the person’s behavior. This is because, even if there is an allergy to a certain substance, if the body is never exposed to it, the signs and manifestations will not be triggered.

In this sense, routine and the environment can facilitate the emergence of allergies when there is a genetic predisposition.

Because if there is sensitivity to dust and the person is constantly in contact with cigarette smoke – which is an irritating agent -, the body can see both as harmful substances.

It goes something like this: the immune system is responsible for the defense of the body. It fights infectious agents or foreign bodies that end up penetrating the body – either through the mouth or nose.

This system is very effective in finding harmful agents. But in the case of people with allergies, there is a small misidentification.

For some reason, there are people who are sensitive to common substances – like smoke, strawberries or dust (which is one of the most frequent allergic causes).

If the hypersensitive body is exposed to them, the defense process begins. Then the leukocytes, which are immune cells present in the blood, are activated and end up overreacting to the substance.

Hyperreactivity produces IgE immunoglobulin, which is a specific type of antibody, and causes the release of histamine, a substance that generates symptoms associated with allergies.

An inflammatory response then occurs to try to protect the body, causing itching, rashes, swelling, sneezing and obstruction of the airways, for example.

How do anti-allergies act in the body?

In order for allergic symptoms to manifest, histamine – a substance released in contact with the allergen agent – must bind to specific receptors, which are proteins that trigger responses in the body.

Antiallergic drugs act by joining the receptors, that is, occupying the space of histamine. Without the possibility of the substance binding to the receptor, the symptoms of the allergy are not triggered.

Histamine acts on different parts of the body, being a mediator of several physiological reactions. In the organism, there are 4 subtypes of receptors, H1, H2, H3 and H4. In summary, they act as follows:

  • H1 : act on smooth muscle contraction (organs), increase vascular permeability, generate itching (itchy skin), decrease blood oxygenation and cause tachycardia;
  • H2 : participate in gastric acid secretion;
  • H3 : controls the release of histamine by the central nervous system (CNS);
  • H4 : participates in the formation of certain cells, such as mast cells and eosinophils (they participate in the body’s immune system).

Because antiallergic drugs work by binding to receptors, each drug has a different target.

The main difference is in the quantity and location of these receptors in our body. While H1 is present throughout the body, H2 is mainly concentrated in the gastric mucosa (stomach).

H1 receptors are the target of antiallergic agents, H2 is for ulcer medications, H3 is potentially target for allergic rhinitis medications and H4 is potentially target for anti-inflammatory and antiallergic agents in autoimmune conditions (such as asthma and rheumatoid arthritis).

Types of antiallergic

In spite of acting, in general, by the same mechanism of inhibition of histamine – preventing the binding of histamine to the receptor -, antiallergic agents can be divided into 2 categories that differ mainly by side effects:

1st generation

First generation antihistamines are also called sedatives or classics . These are the oldest drugs, researched and developed for the longest time.

Although very effective to date, the first drugs developed have a great ability to penetrate the brain region (blood-brain), causing drowsiness and more adverse effects.

The sedative and capacity-reducing effects are so high that it was in the studies of these antiallergic drugs that some antidepressants were discovered.

It is worth pointing out that tricyclic antidepressants and tramadol can potentiate some side effects of the antiallergic, such as drowsiness. The interaction with metoprolol  may increase its action.

Among the most used or most common are:

  • Bronfeniramina;
  • Dexchlorpheniramine ;
  • Chlorpheniramine .

2nd generation

2nd generation antiallergic drugs are more recent, developed from the 1980s.

Although they are continuities of classic antihistamines, they have advantages over the older ones.

As they are less able to cross the blood-brain barrier and have a high affinity for H1 receptors (proteins that bind to histamine and cause allergy symptoms), they generate less side effects, such as drowsiness.

In general, they are drugs that remain in effect for a longer time, when compared to those of the 1st generation.

Among the most used or most common substances are:

  • Cetirizine ;
  • Levocetirizina;
  • Loratadina;
  • Desloratadine;
  • Ebastina;
  • Rupatadina .

When is it recommended to use antiallergics?

There are different types of allergies and they affect a significant percentage of the population. In general, that exaggerated sensitivity to dust, perfume, insect bites, cigarette smoke or food can be alleviated with anti-allergens.

It is worth mentioning that it is always necessary to undergo a medical evaluation and follow the professional’s recommendations, as there are allergies that cannot be treated with antihistamines.

The use of antiallergic agents should always be recommended and guided by a doctor. Among the conditions that may indicate the need for the drug are:

Insect bites (stropula)

Insects are responsible for a significant part of allergies. Sometimes they come from childhood and accompany the person for life. Others, they are punctual, appear after adulthood or occur in the middle of that walk and never manifest again.

Regardless of the case, the insect’s venom can trigger an allergic crisis of varying intensities, but which generally generates redness in the area, itching, reddened plaques throughout the body and, in more intense cases, also affects breathing.


The sinus allergy occurs when regions of the face (sinuses calls) ignite due to allergenic agent. The condition is quite common and can be triggered by exposure to dust mites, pollen, food and chemicals (such as cleaning products).

The patient has very characteristic symptoms, such as pain in the face, a feeling of heaviness around the eyes, headache ( headache ), cough and irritation in the throat, which are common in allergies in general.

Contact dermatitis

Skin irritation occurs due to direct contact with an object or substance. Among those most responsible are latex, synthetic fabrics, metal (such as earrings), perfumes, soaps and make-up.

Allergic rhinitis

The rhinitis allergic is triggered by contact with the irritant agent, which can be dust, smoke or climate change. In general, it triggers respiratory changes, such as runny nose, excessive mucus, nasal stuffiness, coughing and itching in the nose and eyes.

Antiallergic agents are quite effective in controlling crises, but it is worth remembering that they should not be used as the only form of treatment.


Hives can have different causes and, sometimes, be of autoimmune origin, making antiallergic agents not the best treatment option.

However, in some situations they can appear as manifestations of allergic reactions, causing red and intense plaques on the skin that can be minimized with the antihistamine action, as long as recommended by the doctor.

Allergic conjunctivitis

The conjunctivitis allergic occurs in response to exposure to irritants or allergens agents but focuses symptoms in the eye.

As with skin allergies, itching, redness, tenderness, swelling, and uncomfortable sensation (as if there is something inside the eyes) can appear.

In general, antihistamine eye drops are used to alleviate the problem.

Food allergies

There are some substances or foods that generate allergies more frequently, such as milk, eggs, wheat, peanuts, strawberries and seafood.

These allergies can arise at any age, and it is common for a person to become allergic after adulthood, even if they have already consumed the food.

Sometimes, they are punctual reactions – they occur only once – at other times they start to accompany the patient for life.


The cough itself is not an allergy, but a response to the body’s irritation. Coughing can occur mainly in allergic rhinitis, which usually involve irritation of the throat, runny nose and itchiness in the area.

Associated treatments

The use of only one medication is not always effective to control allergic attacks.

In general, it is patients with persistent conditions (such as asthma or allergic rhinitis) who may need joint drug treatments, including corticosteroids and nasal decongestants .

It is worth remembering that the isolated or combined use of medications should only be done under medical guidance.

Although they work to reduce allergies, each one will have different mechanisms:

Nasal decongestants

Nasal drops (nasal decongestants) are topical vasoconstrictor drugs, that is, applied directly to the nostrils and work by contracting the blood vessels of the nasal mucosa.

When the vessels decrease, mucus, swelling and obstructed breathing are also minimized, allowing the patient to breathe better.

According to the Brazilian Association of Allergy and Immunology (ASBAI), the prolonged use of these drugs poses health risks, which can even cause addiction and worsen the obstruction of the nose.


Corticosteroids are substances with anti-inflammatory and immunosuppressive action (they control the response of the immune system).

They can be prescribed in allergic cases, but under specific conditions, as they act in the control of the immune system that can be overly activated during allergies.

Presentation and names of allergy sufferers

There are a number of remedies that can help control the symptoms of allergies. In addition to the active principle – which is the basic substance of the medication’s action -, there are also different ways of presenting the medications, which can be more indicated and facilitate the use according to the cause and location of the allergy:

Eye drops

Antiallergic eye drops are used, in general, by patients suffering from allergic conjunctivitis. They are products with topical and local action, that is, they should only be applied to the irritated eye, according to the expert’s guidance.

Among the options are:

  • Acular;
  • Cromorleg;
  • Lastacaft.


Tablets are oral options that should be taken as directed by a doctor. In general, its action is fast and the effects depend on the class of the drug and its concentration. Among the options are:

  • Loratadina: como Claritin;
  • Dexchlorpheniramine : like Histamin and Polaramine ;
  • Promethazine : as Fenergan ;
  • Fexofenadine : as Allegra and Rafex .

And there is also Prednisone , such as  Ciclorten and Meticorten , which are corticosteroids used in specific allergic events and which require other therapeutic approaches.

Read more: How to take the medicine Prednisone?

Creams and ointments

Antiallergic ointments are topical, that is, they should be applied to the affected region and should not be ingested.

Among the options with antiallergic substances are dexchlorpheniramine maleate – such as Histamin cream – and Promethazine – such as Fenergan cream .

There are also corticosteroid creams and ointments include:

  • Prednicarbate : as Dermatop ;
  • Betametasona : como Withdrew ;
  • Prednisolone : as Predmicin ;
  • Triancinolona Acetonida: como Oncileg A.


Syrups can be used to relieve allergic symptoms that involve coughing or not. Its action is similar to that of the tablet, modifying only the presentation.

It is usually indicated for children or people with difficulty in swallowing pills, for example.

Among the options are:

  • Desloratadine : like Aviant and Deslorana ;
  • Hydroxyzine Hydrochloride : like Prurizin .

Spray nasal

Indicated to relieve nasal symptoms, such as obstruction, common in allergic rhinitis, the sprays are applied directly to the nostrils.

Among the options is the antihistamine Azelastine , with the drugs  Aznite and Rino-Lastin , and the corticosteroids Fluticasone Furoate , as Avamys , and Budesonide , as Budecort Aqua . 


There are anti-allergens that are presented as injectables. In general, they are indicated when the patient does not respond to oral treatment, in acute cases (very severe crises) or in surgeries (in this case, administered by the medical professional).

Among the options are antihistamines such as Promethazine  (as  injectable Fenergan ) and corticosteroids:

  • Betamethasone : as an injectable Diprospan ;
  • Dexamethasone : as an injectable Decadron .


NEVER self-medicate or stop using a medication without first consulting a doctor. Only he will be able to tell which medication, dosage and duration of treatment is the most suitable for his specific case. The information contained in this website is only intended to inform, not in any way intended to replace the guidance of a specialist or serve as a recommendation for any type of treatment. Always follow the instructions on the package insert and, if symptoms persist, seek medical or pharmaceutical advice.

Prices of the most popular anti-allergens

The price of antiallergic agents varies widely, according to the presentation, brand and quantity of the product.

The survey carried out at Consulta Remédios in December 2018 indicated that, on average, prices are between:

  • Eye drops : R $ 9 and R $ 40;
  • Tablets : R $ 8 and R $ 50;
  • Ointments : R $ 3 and R $ 30;
  • Syrup : R $ 10 and R $ 22;
  • Spray nasal: R$ 22 e R$ 38;
  • Injectable : R $ 25 and R $ 60.

They can be found in commercial pharmacies or, to make it easier to compare prices and find better offers, they can be found here .

Children’s antiallergic

Antiallergic drugs are, in general, the same for adults and children, with dosages and constancy of use being the main differences.

Allergies are quite common conditions in childhood – they are sometimes transient and last only a few years or less.

Often, the manifestations begin to appear before the age of 3, making it difficult to administer oral medications. In such cases, syrups may be the best options.

Although medications are very safe during childhood, it is always important to seek medical advice and avoid overuse or unnecessary use of medications.

The ideal is to discover the origin of the allergy and remove the child from the substance or food, avoiding new crises and the need for medication.

When the child has constant or difficult to avoid allergic attacks (such as allergic rhinitis or sensitivity to pollution), the ideal is to invest in auxiliary tactics, such as good hydration, the use of masks, the strengthening of immunity, the use of saline solutions and inhalations.


Contraindications for antiallergic agents include:

  • Use of drugs capable of interfering in the action (such as tricyclic antidepressants);
  • Pregnant and lactating women;
  • Chronic diseases;
  • Children under 2 years old;
  • Central nervous system (CNS) problems;
  • Allergic reactions to the medication itself.

Can pregnant take antiallergic?

It depends . The most modern drugs (2nd generation) are safer and have less side effects. Therefore, for healthy pregnant women, they can be prescribed by the doctor.

Pregnant women who suffer from allergies, such as allergic sinusitis, do not need – and should not – abandon treatment without medical knowledge. However, it is important to know that the use of any medication needs guidance.

The ideal is that the remedies are used as little as possible, especially in the first 3 months of pregnancy, the most appropriate is to avoid the triggering agents.

Read more: Can pregnant women take acetaminophen? Know the dosage and risks

Side effects

The side effects of antiallergic agents depend on each medication and also on the patient’s sensitivity.

According to the concentration of the remedy, side symptoms may appear with greater intensity, including:

  • I’m;
  • Mental confusion;
  • Blurry vision;
  • Alteration of motor capacity (slower movements);
  • Slowness;
  • Nausea and vomiting;
  • Pressure drops;
  • Irritation or restlessness (especially in children);
  • Dry mouth;
  • Urinary retention;
  • Changes in blood pressure (hypotension);
  • Reduced cognitive performance (difficulty concentrating and reasoning).

Drug interactions

The use of antiallergic agents can interact with other medicinal substances, inhibiting or increasing the action of one or both drugs.

In general, any medication that promotes sedative, sleep or calming action can accentuate the effects of 1st generation antihistamines, causing excessive sleepiness and severe depressive state of the central nervous system (CNS).

It is also worth remembering that the 2nd generation have less drug interactions, but that, in general, the most common substances are:

  • Diazepam : for emotional disorders;
  • Ketoconazole : for fungal infections;
  • Erythromycin : for infections;
  • Tramadol : for severe pain;
  • Cimetidine : for gastrointestinal disorders.
  • Phenobarbital : for cases of seizure;
  • Codeine : pain reliever for moderate painters;
  • Tramadol : to treat moderate to severe pain;
  • Clonazepam : for epileptic and mood disorders.

The use of alcohol is not recommended, as it may increase the sedative action of some antiallergic agents.

Interactions with herbal medicines or medicinal plants may also occur. Despite the few studies on the interaction, it is important to note that teas and herbs that promote a sedative or calming effect may have a marked action with the use of antiallergens. Between them:

  • Hyperium perforatum L . : called St. John’s wort or St. John’s wort;
  • Valeriana officinalis L . : call of Valerian;
  • Melissa officinalis L .: known as lemon balm.

Antiallergic gives you sleep?

It depends . The criteria that classify an antiallergic drug as sedative (that is, capable of causing sleep) include 3 factors:

  • Presence of drowsiness;
  • Alteration of cognitive and psychomotor skills (such as concentration and locomotion);
  • Occupation of histamine (H1) receptors above 20%.

Drowsiness and changes in cognitive and psychomotor skills are verified through reports from patients who are still studying the drug.

The occupation of the receptors, on the other hand, is determined by studies on the medicine. For this, specific laboratory tests are used to determine how the substance acts in the body.

In tests, if more than 20% of our specific receptors are occupied by the drug, it has greater side effects.

If the 3 criteria are present, the drug is classified as a sedative. So it is not enough to feel sleepy, as the symptoms can vary for each patient.

In general, 2nd generation antiallergic agents do not affect the motor, cognitive, auditory and mental capacities of the tested patients, and also do not occupy more than 20% of the histamine receptors in the central nervous system (CNS).

It may even be that some people feel drowsy when being treated with a 2nd generation antiallergic, but the symptom is due to the sensitivity of the body.

In relation to the 1st generation, sleep is much more frequent and quite intense, as the drugs are considered sedatives.

Antiallergic and hypoallergenic

When talking about antiallergic it is not always about medication – in fact, the first measure to reduce allergies would be to adopt preventive behaviors against allergic crises, the drugs being used only in emergencies.

A series of actions can have good effects on the routine of patients sensitive to different substances – whether abandoning certain products (such as food) or including others (such as anti or hypoallergenic cosmetics).

Although both have reference to allergies, antiallergic and hypoallergenic are different.

Antiallergic drugs are the drugs used to control the release and action of histamine. In general, they are used after allergic attacks begin and need medical advice.

Hypoallergenic products, on the other hand, are products that, according to ANVISA standards, undergo sensitization tests, ensuring less risk of causing allergies.

For example, hygiene products, makeup and even earrings can be called hypoallergenic. And it is very simple to find this information and choose less irritating products: the information is on the packaging.

Among the options are:

  • Hypoallergenic acetone Franbella ;
  • Davene oat soap ;
  • Dove Serum deodorant ;
  • Creme facial Davene.

But it is worth remembering that there is only a reduction, and does not guarantee that they do not cause allergies.

Natural anti-allergens

Antiallergic agents may be needed in some allergy attacks, quickly reducing symptoms and discomfort. But adopting natural options and preventing manifestations are the best alternatives for health.

Staying away from allergens is not always simple or possible – for example, dust and smoke are difficult factors to avoid completely. Therefore, other measures can be combined with routine, such as:


That drinking water is essential to keep the body functioning is nothing new, but good hydration can play an important role in allergies as well.

Drinking at least 2 liters of water every day helps to reduce symptoms when allergies occur.

In addition, cold baths also help to relieve symptoms. As allergies cause dilation of the respiratory mucous membranes, cold water causes the tissues to contract and makes breathing easier.

Nasal lavage

Nasal lavages are simple, inexpensive and very effective in reducing airway discomfort.

They can be made with saline and are ideal at any age, bringing improvements to breathing even in those drier times of the year.

The application is simple and done directly on the nose: tilt your head and drop 2 or 3 drops into each nostril daily or once a week.

Certain foods

Some foods can be the cause of allergies – in this case, there is no way. You have to eliminate it from the diet. But there are others that can help protect the body and have a more direct action on allergies, such as:

  • Red pepper : it has an expectorant action, which helps to control mucus in the airways;
  • Garlic : contains allicin, which can help to reduce the symptoms of allergic rhinitis;
  • Onion : contains quercetin, a component that can reduce the release of histamine by the body;
  • Chamomile tea : can help to reduce nasal obstruction.

Remembering that they are foods that should be included in the routine without replacing the recommended medical care.

Antiallergic for dog

Like humans, pets are not free to develop allergies. Although the symptoms (and even the causative agent) are the same, the drugs indicated are different and should always be guided by a veterinarian.

Products can be sprays, for topical use (on the skin), or tablets, such as:

  • Cortavance spray  (corticoid) ;
  • Alergovet tablets (antihistamine) .

Common questions

How long does it take for an allergy medicine to take effect?

The effect depends on the medication, but in general, up to 60 minutes after oral ingestion. The duration of the effect varies for each active ingredient, and can last up to 24 hours, as occurs with Loratadine.

Which antiallergic does not give you sleep?

These are 2nd generation drugs that do not give you sleep and do not interfere with the Central Nervous System (CNS). Among them are those made from Azelastine (like Aznite ), Levocetirizine (like Zina ), Loratadine (like Alergaliv ), Fexofenadine (like Altiva ) or Rupatadine (like Rupafin ).

But the ideal is to always consult the doctor or pharmacist and read the package leaflet.

Antiallergic cuts the effect of contraceptives?

No . Contraceptives maintain the normal effect even if taken together with antiallergics. But any medication for occasional or continuous use must be informed to the doctor.

I’m breastfeeding. Can I take antiallergic?

It depends . If the patient undergoes an evaluation and the doctor deems it necessary and safe, some medications can be prescribed with a very strict control and observation.

Antiallergic or antihistamines are medications that help to alleviate various allergic manifestations. The use today has been increasing – accompanying the increase of allergies.

Bringing rapid relief from itching, irritation, skin rashes and respiratory changes, antiallergic agents should always be used under medical guidance to avoid risks to the body.

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