Contact Dermatitis: Irritant Or Allergic – Knowing The Difference

Irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD) are types of contact dermatitis where there is inflammation of the skin caused by direct contact with an offending substance.

Irritant Contact Dermatitis (ICD)

ICD occurs when the skin is damaged by a chemical or physical irritant. Common irritants include detergents, solvents, acids, alkalis and friction.

This reaction is not an allergic reaction and can occur with everybody especially if the irritating substance is applied to skin where there is a disturbed epidermal barrier. This reaction occurs virtually immediately after the application of the irritating substance to the skin. The symptoms and signs are usually confined to the area of contact and these symptoms would include burning, stinging, itching and signs would include redness, swelling and scaliness of the skin.

This is one of the most common adverse reactions reported to our skin therapists on Dermastore support. A frequent scenario is that a new product with active ingredients is applied to the skin where there is a disturbed epidermal barrier (often caused by using harsh cleansers and exfoliators). A good example of this is the retinoid dermatitis i.e. developing an irritant contact dermatitis to the use of a topical retinoid that is introduced too quickly or in too high a concentration. To emphasise once again, this is not an allergic reaction so the topical retinoid dermatitis is transient and the product can be stopped for a period and then can be slowly re-introduced.

Allergic Contact Dermatitis (ACD)

ACD occurs when the skin comes into contact with an allergen which triggers a Type 4 allergic reaction. Common allergens include nickel, fragrances, black hair dye and certain plants. What is important to note is that you have to build up an allergic reaction to the offending allergen, so in other words, after the first exposure nothing will happen but with subsequent exposure to the offending allergen, the allergic reaction will occur.

This allergic reaction only occurs 48 to 72 hours after the offending allergen has been applied to the skin, so the reaction is not immediate. The affected area will be itchy, red, swollen, with scaliness and sometimes blisters.

The allergic reaction may also occur at sites distant from the area of direct contact. This is called an allergic contact dermatitis with an Id reaction or autoeczematisation for example: a woman may become allergic to the nickel in her earrings which would cause a local reaction but she may also develop an itchy rash on the rest of her body.

If a person has been sensitised to the offending allergen, they will remain allergic to this allergen for the rest of their lives so this allergen has to be meticulously avoided in the future.

To ascertain what product the person is allergic to, we as Dermatologists often perform what we call Patch Tests. The European standard battery of patch tests contains about 45 different allergens and these are placed on the persons back under plasters. The results are read by the Dermatologist after 72 hours.

Skincare ingredients that can help with contact dermatitis

• Ceramides
• Panthenol
• Shea Butter
• Oat Kernel Extract
• Beta Glucan
• Lecithin

Skincare products that can help with contact dermatitis

• pHformula SOS Rescue Cream
• ISDIN Nutratopic PRO-AMP® Facial Cream
• Avène XeraCalm A.D Lipid-Replenishing Balm 200ml
• La Roche-Posay Thermal Spring Water
• Mustela Stelatopia Cleansing Gel
• La Roche-Posay Lipikar Balm AP+M 400ml