Patch testing is an investigative process used by dermatologists to determine if someone has developed allergic contact dermatitis (ACD) to something they come into contact with. Early detection of contact allergy through patch testing can ensure that contact dermatitis is managed appropriately, once the cause is identified and eliminated. This in turn prevents the development of a more chronic dermatitis that can be debilitating and potentially impact on a person’s quality of life at work and at home.
Patch testing can be useful to:
- Diagnose or exclude allergy as a cause of contact dermatitis, in both the occupational and home setting
- Determine if contact allergy is playing a role in eczema. For example, in cases where persistent eczema does not improve with treatment, patch testing can be useful to determine if allergy is contributing to an individual’s skin condition.
Patch testing is the gold standard for the diagnosis of ACD. Patch testing can also assist in the diagnostic process in the following scenarios:
- Regional dermatitis: hand, face, eyelid, truncal, anogenital, flexural, foot, airborne or photo distributed sites.
- Suspected occupational dermatitis
- Unexplained flares of atopic dermatitis
- Those with dermatitis that persists despite adequate treatment
- Medications and medical aids e.g. tape, antiseptics, stoma reactions, local anesthetics
- Leg ulcer patients
- Exposure to plants i.e. Phyto-dermatitis
- Exposure to sun i.e. photo-patch testing
- Drug allergy e.g. fixed drug eruption
- Systemic contact dermatitis (with ingestion of allergen producing widespread dermatitis)
- Patients going for joint replacement or post-joint replacement reactions
- Oral mucosal dermatitis/lichen planus
After patch testing, it is important that patients are told about their reactions and the relevance of these reactions. They should also be given written information so they have a clear understanding about their results and also their diagnosis.
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