Written by:  Luke Neill ,  MD (NUEM PGY-3)  Edited by:  Mitali Parmar, MD (NUEM Alum '18)  Expert commentary by : Charles Pearce, MD

Written by: Luke Neill, MD (NUEM PGY-3) Edited by: Mitali Parmar, MD (NUEM Alum '18) Expert commentary by: Charles Pearce, MD


A 7 yo female with no significant past medical history presents with a two-day history of worsening asymmetric rash on the left neck, upper middle chest, right thigh, and the dorsal aspect of both hands. The rash is described as a painful, burning, 3/10 pain and non-pruritic. She denies any history of allergies, especially any allergies to outdoor plants or foods, and denies using any new types of lotions, sunscreen, or other new chemical products. She denies history of trauma. She denies fevers, chills, or recent infections. Denies arthralgias, myalgias, fatigue, or weakness. Denies SOB or chest pain. Denies peeling of her skin or blistering.  She takes no medications.

She is currently attending an outdoor day-time summer camp and her mother first noticed the rash after picking her up at the end of camp two days ago. The mother, due to concern for possible physical abuse would like to know your opinion on its cause. You ask to speak to patient in private and she adamantly denies any physical abuse. You check her vitals.


HR: 65   BP:120/70 Temperature: 96.4 RR:16 O2:100

General: patient well appearing, watching TV

Skin: Multiple small areas of blotchy erythema over left neck, upper middle chest, right thigh, and dorsal aspect of hands in different patterns with no symmetry. Some appear to represent a hand print. The rash on the chest also appears to streak vertically.

Head: normocephalic, atraumatic

HEENT: oral mucosa moist, PERRL, EOM intact, TMs clear bilaterally

Neck: supple, trachea midline

Cardiovascular: regular rate/ rhythm, no murmurs, rubs, or gallops

Chest: non-tender

Pulmonary: clear to auscultation bilaterally

GI: non-distended, soft, non-tender 

MSK: no deformities

Neuro: CNII-XII intact, strength/sensation grossly intact

Skin Exam: 

Screen Shot 2018-09-14 at 10.48.31 PM.png

Labs: CBC and BMP Unremarkable

Clinical Course:

In consultation with dermatology, patient revealed that she recently made limeade at her summer camp about 2 days prior to arrival, and had been out in the sun for outdoor activities. Given this history and appearance of the rash, the patient was diagnosed with phytophotodermatitis, and discharged home with instructions to stay indoors. She was seen in clinic after 5 days, and had developed multiple blisters over her hands, chest and thighs. The rash subsequently completely resolved in 2 weeks time.



Phytophotodermatitis, also known as “Lime Disease” or “Margarita Photodermatitis” is a phototoxic inflammatory eruption of the skin that occurs due to contact with light-sensitizing botanical substances and subsequent exposure to UV-A radiation. Interestingly, the reaction of phytophotodermatitis is actually independent of the immune system.

But How?

When furocoumarins, the photosensitizing chemical compound produced by certain plants, are struck by a photon in the UV-A range of (320-400), energy is absorbed causing the formation of an excited state from ground state. When the furocoumarin returns to ground state, energy is released in the form of heat and fluorescence, leading to both DNA and RNA damage and cell death.

Furocoumarin is present in:

  • Limes

  • Figs

  • Parsley

  • Celery

  • Carrots


  • Skin eruption typically begins 24 hours after sun exposure


  • Burning erythema with blistering

  • Post-inflammatory hyperpigmentation lasting weeks to months. 


  • Eruption peaks at approximately 48-72 hours


Below is an image illustrating the progression in days, of a person with phytophotodermatitis of the hand:


As phytophotodermatitis occurs independent of the immune system; any race, sex, or age group may be affected. However, it does appear that produce workers in grocery stores are at a much higher risk than the general population. A 1986 study showed that in one un-named nationwide grocery store chain, a randomly selected sample of all its stores revealed phytophotodermatitis occurrence in 13 of 17 states, with occurrence in 26% of the produce workers surveyed. In this instance, it was thought to be due to celery stock with higher levels of endogenous furocoumarin.


The prognosis of phytophotodermatitis is very good with proper identification and elimination of the offending plant. Patients who are affected should stay indoors avoiding UV-A rays to allow the dermatitis to self-resolve. 

Note: This is not the first time phytophotodermatitis has mimicked child abuse. A 1985 study looked at two separate cases of children who were initially thought to have hyper-pigmented skin lesions suggestive of child abuse and were later given a final diagnosis of phytophotodermatitis.

Takeaways/Learning Points:

  • Consider phytophotodermatitis in your differential for rash in summer months.

  • Although we ask about allergies, consider asking about recent food exposure.

  • Don’t spill your drink!

Expert Commentary

Great overview of phytophotodermatitis!  This is certainly a fascinating and easily missed phenomenon given its relative rarity, variable pattern of presentation and, on occasion, insidious exposures. In the Midwest, we are seeing additional exposure risks to phytophotodermatitis in the form of Wild Parsnip (known colloquially as poison parsnip), an invasive plant that was introduced from Europe over a century ago and whose range has continued to expand.  This expansion has lead to Department of Natural Resource and local media in a number of states working to educate the public as well as local and regional medical facilities about the potential threat.

As with lime juice, exposure to the sap of Wild Parsnip can be potentially non-apparent to the patient and the clinician.  In fact, the pattern of burns from Wild Parsnip are as variable as the methods of exposure- from linear lesions from unwittingly brushing against a plant to extensive hand/forearm involvement from attempted manual removal of a plant to a speckled burn pattern from mechanical disruption of the plant (think weed whacker or lawn mower).  This variability obviously heightens the diagnostic difficulty and uncertainty. 

Another consideration and as noted in your excellent review, phytophotodermatitis is a burn resultant of chemically induced cell death by cross linkage of the furan ring with pyrimidine bases in the presence of UV light.  And recognition of this phenomenon as a chemical burn does have bearing on management. A discussion with or referral to burn centers may be warranted, as with any burn, if there is significant TBSA involvement or depending on body area impacted.  And looking for and warning patients of the potential for super-infection is imperative.

As a ER physicians in rural Wisconsin, our practice sees a couple handfuls of phytophotodermatitis cases each summer.  Our local communities (namely farmers) are well aware of Wild Parsnip and the simple prevention of avoidance and washing exposed areas to remove sap.  As more and more people (hopefully) continue to venture out of cities and explore the hiking, biking and nature trails of the rural Midwest, broadening public awareness of a potentially painful exposure matters and so thank you for the chance to respond to your fantastic blog!


Charles Pearce, MD NUEM ’14

Madison Emergency Physicians

How to Cite This Post

[Peer-Reviewed, Web Publication]   Neill L, Parmar M (2018, September 24). Phytophotodermatitis.  [NUEM Blog. Expert Commentary by Pearce C]. Retrieved from

Other Posts You May Enjoy


  1. Berkley SF, Hightower AW, Beier RC, et al. Dermatitis in grocery workers associated with high natural concentrations of furanocoumarins in celery. Ann Intern Med. 1986 Sep. 105(3):351-5. 

  2. Coffman K, Boyce WT, Hansen RC. Phytophotodermatitis simulating child abuse. Am J Dis Child. 1985 Mar. 139(3):239-40.

  3. Marcos LA, Kahler R. Phytophotodermatitis. Int J Infect Dis. 2015 Sep. 38:7-8. 

  4. Smith E, Kiss F, Porter RM, Anstey AV. A review of UVA-mediated photosensitivity disorders. Photochem Photobiol Sci. 2011 Dec 16. 11(1):199-206. 

  5. Becker, M. (2017). Phytophotodermatitis Rash [Digital image]. Retrieved November 10, 2017, from’t-mix.

  6. Kid, K (June 3, 2015) Phytophotodermatitis From Exposure to Lime Juice [Digital image]. Retrieved November 10, 2017, from



Posted on September 24, 2018 and filed under Dermatology.