Also, it is possible that the skin lesion does not take the form of a rash but it may include papules, blisters, vesicles or even a simple red area.

[2] Once an individual has developed a skin reaction to a certain substance it is most likely that they will have it for the rest of their life, and the symptoms will reappear when in contact with the allergen.

This classification differs from the more prevalent Type I hypersensitivity (e.g., hay fever), where allergens bind to antibodies, that subsequently trigger mast cells.

This complex of allergen and carrier protein is what the immune system detects as foreign, leading to an allergic response.

This process is controlled by cytokines and chemokines – with tumor necrosis factor alpha (TNF-α) and certain members of the interleukin family (1, 13 and 18) – and their action serves either to promote or to inhibit the mobilization and migration of these LCs.

It has also been proposed that the vehicle in which the allergen reaches the skin could take some responsibility in the sensitization of the epidermis by both assisting the percutaneous penetration and causing some form of trauma and mobilization of cytokines itself.

[citation needed] This is due to local skin memory T-cells, which remain in the original sensitization site.

In some cases doctors can establish an accurate diagnosis based on the symptoms that the patient experiences and on the rash's appearance.

According to the American Academy of Allergy, Asthma, and Immunology, "patch testing is the gold standard for contact allergen identification".

[18] After two days, they are removed and if a skin reaction occurred to one of the substances applied, a raised bump will be noticeable underneath the patch.

Corticosteroid creams should be used carefully and according to the prescribed directions because when overused over longer periods of time they can cause thinning of the skin.

Also, in some instances such as poison ivy dermatitis calamine lotion and cool oatmeal baths may relieve itching.

Commonly, the symptoms may resolve without treatment in 2 to 4 weeks but specific medication may hasten the healing as long as the trigger is avoided.

Allergic dermatitis of the hands is often due to contact with preservatives, fragrances, metals, rubber, or topical antibiotics.

[5] Dermatitis at the front of the face is often due to gold (from jewelry and foundation), make-up, moisturizers, wrinkle creams, and topical medication.