From Dr Fonacier - Antibiotics, steroids, anesthetics, antifungals, preservatives and the vehicle itself can be common contact sensitizers in drugs. Patch testing for contact drug allergies - if you don’t do a reading at day 7, 30% of topical corticosteroid allergy may be missed. If you don’t do 7-day read on patch test, may miss up to 30% of topical corticosteroid contact derm. also 3 agents in TRUE test will detect majority per Dr Foncier. Good to know.
Baboon Syndrome - Most recognizable form of systemic CD with erythema of buttocks and upper thighs. Most common cause are nickel and Balsam of Peru but can be due to drug allergies, both topical and systemic drugs.
Cobalt is main component of Vit B12 - if sensitized to cobalt, Vit B12 can cause systemic contact dermatitis.
Topical antihistamines are common sensitizers and can trigger topical contact dermatitis but also systemic contact dermatitis from oral ingestion.
Patch testing with drugs may be helpful in DRESS, AGEP, SJS/TEN, and fixed drug eruptions. If patch testing with pure drug, do in 10% petrolatum or 10% alcohol. If using commercial prep of drug, grind drug and test 3 forms, as is, 30% petrolatum and 30% in water.
Systemic contact dermatitis has been described in formaldehyde sensitive patients who ingest aspartame. Also, aspartame (a sweetener) is in chewable montelukast per Dr Fonacier.
Routine preimplantation (orthopedic) patch testing to metals not indicated in patients who deny prior symptoms to metals. Consider in pts with hx c/w metal allergy. Orthopedic implants - Joint failure (joint loosening or pain) and dermatitis can both be due to metal allergy. Rule out infection as a cause of joint failure first.
SJS and DRESS
Use of TNF inhibitors (ie enterancept) have been described for use early in SJS/severe cutaneous adverse reactions - Dr Sidbury.
And another pearl from the rash talk—up to 40% of DRESS patients may not have eosinophilia, despite being the ‘E’ in the name DRESS.
Onset of AGEP (acute generalized exanthematous pustulosis) often has onset in as little as 1 day. Notably different from other SCARs.
This is a Twitter summary from #ACAAI18 meeting based on tweets by the following allergists: @mrathkopf @karrenrobinsmd
Diagnosis of Pruritus (Itching) (click to enlarge the image).