Allergic and irritant contact dermatitis

Contact dermatitis is an eczema that can cause reddening, dandruff and itching, sometimes burning and tingling on the skin.

This disease leads to:

Contact dermatitis occurs a few hours after contact with irritating substances or allergens.
The reaction of the skin persists for a few days if the skin has no further contact with this allergen.

In more severe cases, allergic contact dermatitis can progress into generalized rashes (all over the body).
Normally, swallowing an allergen is harmless, but it can cause:

  • “Baboon syndrome” (SDRIFE), the redness of the skin on the buttocks, groin, flanks and top of the thighs;
  • systemic generalized contact dermatitis.

Contact dermatitis should be distinguished from contact urticaria, in which a rash develops a few minutes after exposure and then passes again in a few minutes or hours.
The allergic reaction to latex is probably the best-known example of allergic urticaria.
The rash can become infected if the affected person scratches and irritates the skin lesions.


Types of dermatitis

There are two forms of contact dermatitis, which differ in the mechanisms that provoke the inflammatory response, but the symptoms may be identical.

  1. Irritant contact dermatitis arises at the point where an irritating or toxic chemical substance comes into contact with the skin.
  2. Allergic contact dermatitis is an itchy rash that develops only in people who have an allergic sensitivity to a particular substance.
    These substances are not necessarily irritating or toxic.
    They can induce an immune response on the skin at the site where there is direct contact with it.
    Dermatitis develops only if there has previously been (sensitization) contact with this substance. In this way, the immune system is given the opportunity to react to this substance when a new encounter takes place.

How does allergic contact dermatitis manifest itself?

Usually, dermatitis is limited to the area of contact with the allergen, although in the most severe cases it can extend or generalize beyond that.
Sometimes the allergen is transported from the fingers to other areas of the body, for example:

  • to the eyelids,
  • in the genital area.

Some examples of allergic contact dermatitis are:
1. Eczema on the wrist under a bracelet due to allergy to nickel contact.
2. Eczema on the leg after removal of an ankle bandage due to contact with adhesive resin.
3. Hand eczema caused by chemical substances used in latex gloves.
4. Dermatitis on the outer ear caused by earrings (allergic reaction to nickel).
5. Red spots on the face and itching due to contact allergy with methylisothiazolinone, a preservative in shampoos and facial tissues.

How does irritant contact dermatitis manifest itself?

Possible forms of irritant dermatitis:

  • Acute: it appears like a sudden burn with redness and sharply defined blisters. It is a typical reaction to the contract with an extremely toxic substance such as acid.
  • Chronic: it appears as itchy erythema and diffuse scaling in the contact area. The reaction is caused by repeated contact with less irritating substances such as soap or shampoo.

Causes of irritant and allergic contact dermatitis

Irritant contact dermatitis is the most common type (80% of cases).
It arises upon contact with:

  • Acids
  • alkaline substances such as soaps, detergents and fabric softeners,
  • Solvents and other chemicals.

Other irritating substances may be:
1. cement;
2. hair dye;
3. contact with wet diapers that irritate the buttocks of toddlers and infants;
4. pesticides and herbicides;
5. Latex gloves;
6. some cleansers such as chlorine or skin cleansing products, which can also cause irritation of the genitals;
7. Shampoos, but also just water, can cause dermatitis on the scalp.

The substances that cause irritant contact dermatitis can become allergenic and lead to hypersensitivity.

Allergic contact dermatitis is caused after exposure to substances and materials to which the person is hypersensitive or allergic.
Contact dermatitis is not contagious.

The most common allergens are:
1. adhesives, including those used for false eyelashes or wigs;
2. antibiotics such as neomycin;
3. Peru balsam (used in many personal care products and cosmetics, as well as food and beverages);
4. Products for the processing of fabrics and garments containing potassium bichromate, which is present in leather and hides;
5. fragrances in perfumes, cosmetics, soaps and moisturizers;
6. Sweat, especially in the genital area, where rashes are mainly caused by synthetic washing;
7. Nail polish, hair dye and perm solvents containing formaldehyde;
8. Nickel or other metals contained in:

  • Jewellery
  • Bracelets
  • Metal zippers
  • Bra clasps
  • Coins
  • Pocket knives
  • Lipstick containers and powder boxes

9. Poisonous ivy and other plants such as:

  • Cypress family
  • Tree of God (Ailanthus))
  • Boxwood
  • Privet
  • Peony
  • Arnica

10. milk of the fig tree;
12. gloves made of rubber or latex;
13. some footwear, especially sneakers, because of the rubber and resins used.

You cannot have an allergic reaction at the first contact with a substance, this requires regular contact over a period of 5-21 days.

Photoallergic dermatitis
Some products cause a photoallergic skin reaction in connection with sun exposure.
These substances include:

  • Aftershave
  • Sunscreen
  • Medications such as:
    • antibiotics (tetracyclines, quinolones),
    • ointments containing sulfamide,
  • some fragrances and deodorants containing alcohol,
  • lemon peel, bergamot and lavender oil,
  • Products with tar and coal.

Some allergens, such as ragweed (ragweed) or insect sprays, can cause contact dermatitis.

Diagnosis and tests in contact dermatitis

The diagnosis basically results from:

  • the appearance of the skin,
  • the questions about the irritating substances and allergens that came into contact with it.

Patch test The patch test (patch test
) determines the allergens that provoke a reaction.
The patch test is used in patients suffering from recurrences of chronic contact dermatitis.
Three practice visits are required here; the test must be performed by trained and experienced health professionals to interpret the results correctly.
The evaluation of the patch test takes place 48 and 96 hours after application.

  1. At the first visit to the practice, small amounts of the material containing the possible allergens are applied to the skin of the back by means of plasters.
  2. At the second doctor’s visit, the patches are removed (after 48 hours) to observe a possible reaction.
  3. third field visit is made two days later (96 hours after application) to verify a late reaction.

The patch test may be helpful in distinguishing irritant contact dermatitis from allergic:

  • Irritant dermatitis passes on its own in the course of 1-2 days.
  • Allergic dermatitis persists for many days.

Other tests can also be used to rule out possible causes, including a skin biopsy.

For differential diagnosis, it is necessary to consider:

  • Neurodermatitis
  • photoallergic dermatitis,
  • seborrheic dermatitis.