Contact Dermatitis and Skin Allergy

What it is

Contact dermatitis is a type of eczema triggered by contact with a particular substance. [1] The skin becomes itchy, blistered, dry and cracked, usually within hours or days of exposure, and the hands and face are most often affected. [1] Color changes depend on skin tone: lighter skin becomes red, darker skin can become dark brown, purple or grey. [1]

Two types

• Irritant contact dermatitis is the most common type. It is the skin's reaction to irritating substances or friction, such as soaps, detergents, solvents, and frequent contact with water. [2][1] It is usually more painful than itchy. [3]
• Allergic contact dermatitis is an immune reaction to a substance such as fragrances in perfumes, cosmetics, soaps and moisturizers, nickel, rubber or latex, hair dyes, nail polish, preservatives and some plants. [2]

MedlinePlus says you will not react the first time, but sensitization can build with repeated exposure, an allergy can appear after years of tolerance, and once an allergy develops it is lifelong. [2] The reaction most often appears 24 to 48 hours after exposure and can last for weeks. [2] Some products cause a reaction only with sun exposure. [2] Hairstylists and others who handle irritants or allergens at work are at higher risk. [3]

Established care

The NHS says contact dermatitis usually improves or clears when the cause is found and avoided. [1] Rinse affected skin with warm water and an emollient as soon as possible, protect hands with gloves (taking them off now and then because sweating can make symptoms worse), swap products that irritate, and moisturize often. [1] Doctors may prescribe steroid creams for severe symptoms. [1] This is an established recommendation.

Patch testing

If an allergy is suspected, a provider may do a patch test: small patches containing specific allergens stay on the skin for 48 to 96 hours, must be kept dry, and are then removed and checked for reactions. [3] MedlinePlus says patch testing is used for people with long-term or repeated contact dermatitis, takes at least 3 visits, and must be done by a provider skilled at interpreting results. [2] The American Academy of Dermatology says results can help identify the cause so you can avoid it. [4]

Limits to know: there is no test for irritant contact dermatitis; diagnosis rests on the exam and your history. [3] Patch tests identify allergy, not irritation. For essential oils, a review suggests people be tested with their own products where possible. [5] The sources read describe patch testing done by a provider. Proper evidence not found for a validated at-home patch test in the sources checked, so a dab of product on the forearm should not be treated as proof that a product is safe.

Natural products

"Natural" ingredients can be allergens. A review found nearly 80 essential oils have caused contact allergy, mostly with pure oils or high-concentration products. [5] See Essential oil safety and Natural ingredient safety.