Contact dermatitis and patch testing for the allergist - Twitter summary from 2013 #AAAAI meeting

This summary was compiled from the tweets posted by allergists/immunologists who attended the 2013 annual meeting of the American Academy of Allergy Asthma and Immunology (AAAAI) (see the list at the end). The tweets were labeled #AAAAI. The text was edited and modified by me.

With contact dermatitis, history is extremely important. Patch testing recommended in all cases of chronic hand eczema given high positive predictive value for contact allergy. Suspect venous stasis as a contributing factor for leg dermatitis when lesions worsen or fail to respond to topical steroid treatment.


Dr Luz Fonacier spoke first on cosmetics.

The average adult uses 12 personal hygiene products per day. Cosmetics are now being marketed to children. Some cosmetics (esp mascaras) are contaminated with nickel.

Most affected site of ACD (allergic contact dermatitis) from nail varnish is the neck. Most common ACD chemicals are fragrances.

Balsam of Peru

Food related contact dermatitis from balsam of Peru (gums, mouthwash, toothpaste) can also cause hives with tomato-containing products. Here is a list of foods containing balsam of Peru

Tomato ACD is associated with balsam of Peru. The balsam is often implicated in systemic contact dermatitis rather than localized.

Common rashes - 2-minute video overview by a dermatologist for


How to avoid formaldehyde resins - wear 100% silk, polyester, acrylic, nylon, etc. (baggy clothes).

Resin in shin guards and neoprene can cause allergic contact dermatitis (ACD) reactions.

PPD allergy

PPD is found in hair dye, body painting and temporary tattooing (like henna). PPD sensitization is life long!

Alternatives to PPD are semi-permanent dyes based from vegetable oils.

Patch testing

With the current T.R.U.E. test, you can still miss 27% of clinically relevant allergens. Typical chemicals missed by the current TRUE test include propolis, fragrance mix II, DMDM hydantoin, cinnamic aldehyde, iodopropynyl.

So, if you have a negative patch test (35% of patients) - ACD is still possible, and you need to do more tests, and consider irritant contact dermatitis, and other diagnoses. Biopsy may be indicated.

A negative patch test is reassuring, but positive patch test doesn't prove that a serious complication is due to ACD.

TRUE testing during pregnancy? Speakers say avoid it.


Luckily, ACD is rare with pacers and defibrillators.

Nickel ACD

Nickel is the #1 agent in contact dermatitis. A lichenified plaque on the abdomen is a classic presentation of nickel ACD. However, nickel can also cause systemic reactions.

Nickel sensitization may be related to dietary nickel intake.

Nickel is most common ACD allergen in orthodontics. Nickel allergy can cause systemic plaques (remote from contact site) if continued nickel contact despite local symptoms.

Nickel ACD is usually a permanent sensitivity.

In gynecological implants, the most common metal is copper.

Pre-implantation eval (patch testing) should only be done with those with previous history of ACD.

Occupational ACD

About 15.5% of lifetime is spent at work, so workplace exposures do cause significant dermatitis.

MSDS sheet

Often, manufacturers of patch tests provide standardized panels for various professions (dental, metal workers, etc). Reading a MSDS sheet is a helpful skill for allergists to have. What to look for in MSDS - reactive components, cleaning compounds, metals.

You can use the actual materials from work, dilute if needed, test to components separately and together. An irritant control may be an issue.

Many chemicals implicated in ACD can also cause asthma if you inhale them (eg in machine operators, metal working fluids, glues).

Joint prostheses and ACD

Dr. Pacheco discussed hip, orthopedic and medical devices. Joint prostheses go back to ancient Egypt!

No pre-implantation testing is necessary for patients without a solid history of metal sensitization.

The need for revision in joint replacement is 7%, It is rare that allergy is a cause of revision, mostly they are related to infection, biomechanical failure, etc.

The presentation with ACD from metal joint replacements is not typically localized rash - it is mostly with pain, chronic effusion, etc.

The stainless steel composition is 10-24% Ni, 18% Cr, 65% Fe.

Bone cement is mainly methyl methacrylate, but it may contain other chemicals too (it can even be antibiotic-infused). Methyl methacrylate was once used in artificial nails but it has been removed due to asthma and ACD concerns - but it is a great joint cement!

Both bone cement and spacers are made from methyl methacrylate in replacement joints.

John Browning discussed contact and irritant dermatitis.

Malassezia dermatitis is found on head, neck and upper trunk. Lanolin in Aquaphor (a common cream used in AD) can cause allergic contact dermatitis (ACD).


Photodermatitis presents with hyperpigmented marks after sun exposures due to a phototoxic reaction.

Phytophotodermatitis is an irritant contact dermatitis from squeezing citrus fruit in the sun - it causes postinflammatory hyperpigmentation.

ACD to mangos is itchy rash around the mouth due to urushiol (in peel and sap).

Tomato ACD is associated with balsam of Peru. The balsam is often implicated in systemic contact dermatitis rather than localized.

Perioral dermatitis can be due to spacers for asthma, ICS or topical steroids.

PTBP-FR dermatitis can be due to sports gear, foam (in bras), wet suits, etc. Sensitization by para-tertiary-butylphenolformaldehyde resin (PTBP-FR), which is particularly useful as a leather glue, has been known for 30 years (

“Toilet seat dermatitis"

“Toilet seat dermatitis" - location matches where they sit on the toilet - this is an irritant reaction from cleaning solutions on toilet seat.

Toilet seat dermatitis is usually secondary to an irritant reaction (chemical cleaners) but can be due to urushiol exposure.

Allergists are on Twitter - follow them

Allergists increased Twitter use 470% in one year - 25 allergists reached 250,000 individuals from the 2012 #AAAAI meeting (see the references here). This summary was compiled from some of the tweets posted by the following allergists:

This is a list of the allergists who used Twitter to post updates from the 2013 #AAAAI meeting. The list is open for edit, please feel free to add your own info.

I would strongly encourage you to post updates on Twitter from the CME conferences that you are planning to attend in the future. Here is how to do it: Twitter for Physicians: How to use Twitter to keep track of the latest news and scientific meetings, and share information with colleagues and patients.

Disclaimer: The text was edited, modified, and added to by me. This is one of a series of posts that will be published during the next few weeks.

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