Allergic contact dermatitis, also referred to as contact hypersensitivity, is mediated by CD8+ T cells, which are primed in lymphoid organs during the sensitization phase and are recruited in the skin upon re-exposure to the hapten.
What is the mechanism of contact dermatitis?
Contact dermatitis is an inflammatory eczematous skin disease. It is caused by chemicals or metal ions that exert toxic effects without inducing a T-cell response (contact irritants) or by small reactive chemicals that modify proteins and induce innate and adaptive immune responses (contact allergens).
What is the pathophysiology of allergic contact dermatitis?
The pathophysiology of allergic contact dermatitis starts with the contact of the allergen to the skin. This allergen penetrates that stratum corneum of the skin and is taken up by Langerhans cells.   The antigens subsequently undergo processing by these cells and get displayed on their surface.
What is the most common cause of allergic contact dermatitis?
Nickel. Nickel is the most frequent cause of allergic contact dermatitis.
What type of reaction is seen in allergic contact dermatitis?
Allergic contact dermatitis is a type 4 or delayed hypersensitivity reaction and occurs 48–72 hours after exposure to the allergen. The mechanism involves CD4+ T-lymphocytes, which recognise an antigen on the skin surface, releasing cytokines that activate the immune system and cause the dermatitis.
How is allergic contact dermatitis diagnosed?
For suspected cases of allergic contact dermatitis, a series of tests called patch testing can identify the underlying cause of allergic contact dermatitis. With a patch test, you wear adhesive patches on your skin. The patches contain chemicals known to commonly trigger allergic reactions.
What is the difference between allergic and irritant contact dermatitis?
Irritant contact dermatitis is caused by the non–immune-modulated irritation of the skin by a substance, leading to skin changes. Allergic contact dermatitis is a delayed hypersensitivity reaction in which a foreign substance comes into contact with the skin; skin changes occur after reexposure to the substance.
How does dermatitis develop?
A common cause of dermatitis is contact with something that irritates your skin or triggers an allergic reaction — for example, poison ivy, perfume, lotion and jewelry containing nickel.
What is the treatment for allergic contact dermatitis?
A steroid ointment may be applied one or two times a day for two to four weeks. Or try calamine lotion. Take an oral anti-itch drug. A nonprescription oral corticosteroid or antihistamine, such as diphenhydramine (Benadryl), may be helpful if your itching is severe.
What causes dermatitis on hands?
What causes hand dermatitis? In many people, hand dermatitis happens because of direct damage to the skin by harsh chemicals as well as irritants, especially soap, detergent and repeated contact with water. This is called irritant contact dermatitis.
What’s the difference between eczema and contact dermatitis?
For example, many doctors use the terms “atopic dermatitis” and “eczema” interchangeably but wouldn’t use the term “contact dermatitis” in place of “eczema.” Dermatitis means inflammation of the skin. Eczema is inflamed skin that has other symptoms like itching, a flaky or scaly rash, and dry skin.
Is allergic contact dermatitis an immediate reaction?
Contact allergies can lead to severe skin reactions. Unlike with many other kinds of allergies, the reaction doesn’t occur immediately, but usually after one to three days.
What is a Type 4 allergic reaction?
Type four hypersensitivity reaction is a cell-mediated reaction that can occur in response to contact with certain allergens resulting in what is called contact dermatitis or in response to some diagnostic procedures as in the tuberculin skin test. Certain allergens must be avoided to treat this condition.
What are the stages of an allergic reaction?
The human body carries out an allergic cascade in three stages: sensitization, “early-phase,” and “late-phase.”