From the Guidelines
Dermatologic conditions mediated by type IV hypersensitivity reactions include allergic contact dermatitis, which is a common condition in individuals with atopic dermatitis, with a prevalence of 6-60% of subjects depending on the study, as reported by 1. These reactions occur when allergens like nickel, fragrances, or preservatives contact the skin and activate sensitized T cells, leading to an inflammatory reaction.
- Allergic contact dermatitis is often clinically indistinguishable from atopic dermatitis and should be considered as an alternative diagnosis or a concomitant condition.
- The most common contact allergens in atopic dermatitis patients include nickel, neomycin, fragrance, formaldehyde, and other preservatives, lanolin, and rubber chemicals, as noted in 1.
- Diagnosis of allergic contact dermatitis is by patch testing, which has a sensitivity of 60-80% in reports, and should be considered in cases where a history and/or physical exam is suggestive of the condition, such as disease aggravated by topical medications or emollients, or patterns that reflect application of, or exposure to, a consistent item.
- Management of allergic contact dermatitis generally involves identifying and removing the triggering agent, using topical or systemic corticosteroids to reduce inflammation, and in severe cases, employing immunosuppressive medications, as discussed in 1.
From the Research
Dermatologic Conditions Mediated by Type IV Hypersensitivity Reaction
- Contact dermatitis is a common inflammatory skin disease caused by exposure to contact allergens and irritants, and it can be mediated by a type IV hypersensitivity reaction 2.
- Type IV hypersensitivity reactions are a type of hypersensitivity reaction that involves T cells and can cause a range of dermatologic conditions, including contact dermatitis and severe cutaneous adverse reactions (SCARs) 3, 4.
- SCARs are a group of dermatologic diseases that result from a type IV hypersensitivity process and include drug reaction with eosinophilia and systemic symptom (DRESS) syndrome, Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), and acute generalized exanthematous pustulosis (AGEP) 4.
- Atopic dermatitis is a chronic relapsing and remitting inflammatory skin disease that can be associated with contact dermatitis, but it is not typically mediated by a type IV hypersensitivity reaction 5, 6.
- Psoriasis is another skin condition that can be associated with contact dermatitis, and it may also involve type IV hypersensitivity reactions, although the exact mechanisms are not fully understood 6.