“Allergic to anything?”

How many times have you uttered that question, only to sigh inwardly at the replies of “hard work, doctor,” “Ooh dandelions, they make my eyes water something dreadful,” and my personal favourite – “strawberries and Fairy Liquid” … You contemplate asking: “How likely is it that we are going to be treating your incarcerated hernia with strawberry jam, Mr Jones?” You smile and carry on with your history.

Of course, some clinicians may argue that this is the most important question you can ever ask a patient. God forbid you should be fast bleeped to the wheezy patient with a rash and plummeting blood pressure. But I’m not going to write an article about penicillin induced anaphylaxis, important though it is. I’m going to tell you about one of the weird and wacky answers a patient once gave to that question…

Ok fine I’m the patient. And I’m allergic to light.

Solar urticaria is a rare photodermatosis affecting an estimated 1 in every 300,000 people worldwide. It is characterised by pruritus, stinging, erythema, and wheal formation within seconds or minutes of exposure to sunlight or an artificial light source emitting the appropriate wavelength (1).

Solar urticaria can be primary or secondary. Primary solar urticaria is an immediate IgE mediated hypersensitivity response towards an allergen which is induced in the body following exposure to light. Rarer still, secondary solar urticaria can occur in association with other disorders, such as cutaneous porphyria or lupus, or with a plethora of commonly used medications known to cause photosensitivity, such as tetracyclines, NSAIDs, and quinine (2,3).

I suddenly developed this most peculiar allergy whilst on holiday during my first year at medical school. Having only very rarely suffered from sunburn in the past, I was somewhat surprised when after five minutes of sun exposure I swiftly erupted in intensely itchy and painful urticarial wheals that covered every inch of my exposed skin.

Subsequent photo-testing with different wavelengths of light demonstrated an extreme allergy to visible wavelengths of light. Most people with SU are allergic to ultraviolet (UV) light, and can use UV filtering sun creams to good effect. I however, must rely on a cocktail of antihistamines and immune suppressants in order to live a “normal” outdoor life. Despite these treatments, activities such as picnics, music festivals, and going to the beach are a distant memory. I spend two to three weeks of the year in hospital having a desensitisation treatment called Narrowband UVB1 which involves standing naked in a Tardis-like light box. This method of “toughening of the skin” allows me to spend short periods of time outside in the spring and summer, but when my allergy is bad, indoor light bulbs and computer and television screens set me off. Too much skin reacting leaves me woozy and fatigued, unable to do more than flop on the sofa and whinge at passing housemates.

It’s difficult explaining my often blotchy appearance to patients and colleagues, and even most doctors only have a hazy recollection of their medical school dermatology. Passers by often stare at my heavy black umbrella, up in the sunshine, and I have had complete strangers scold me for getting sunburnt.

But there are advantages too, my lifestyle means I’m hardly likely to develop skin cancer, and while all my sun seeking friends will be splashing out on anti-wrinkle creams in 15 years time, I shall be smug in my hopefully wrinkle free skin. Doctors can’t predict if my weird and wonderful allergy will improve with age or deteriorate.

Hopefully I’ll be able to fulfil my dreams of becoming a haematologist but perhaps I’ll have to be a radiologist in a darkened room in the hospital’s cellar! Despite all this self-pity, I still count myself lucky. There are people with solar urticaria who can’t leave their homes; children living in foil lined space-suits who have to go to night-time activity camps.

One glimmer of hope for a cure lies in the melanocyte stimulating drug afemelanotide,
developed by Clinuvel Pharmaceuticals and currently in phase III trials in patients with other forms of photosensitivity. Originally developed with a view to induce a tan that would protect against skin cancer, the drug is being trialled in the US in photosensitive porphyria patients who, like me, might benefit from a chemically induced healthy glow. (4) I await the results with bated breath.

So we return to clerking Mr Jones et al. When I ask patients about their allergies and they reply with strawberries, Fairy Liquid, or sticky-back plastic, I too smile and sigh. But I also try and remember to think – what if they happen to be a strawberry farmer, dishwasher, or Blue Peter presenter? How might their allergy affect their lives and livelihoods? We are all aware that allergy is dramatically increasing in prevalence. (5) It’s is an important issue for patients who suffer from difficult to manage allergies, and it should be important to their doctors too. Perhaps it’s time for allergy to deserve more than four capital letters on your history sheet.

1. Tajirian A.  Solar urticaria. 2009 http://emedicine.medscape.com/article/1050485-overview
(accessed 10 October 2010).
2. Clinuvel.  Solar urticaria. 2010 http://clinuvel.com/skin-conditions/rare-skin-conditions/solarurticaria
(accessed 10 October 2010).
3. BNF Online. 2010 http://bnf.org/bnf/ (accessed 10 October 2010).
4. Health USNIo. Phase III confirmatory study in erythropoietic protoporphyria (EPP). 2009.
http://clinicaltrials.gov/show/NCT00979745 (accessed 10 October 2010).
5. Law M, Morris JK, Wald N, Luczynska C, Burney P. Changes in atopy over a quarter of a century,
based on cross sectional data at three time periods. BMJ 2005; 330: 1187.

Athalia Pyzer is a 5th year medical student at the University of Birmingham.