Sun Bumps
By Tod Schimelpfenig
Curriculum Director – WMI of NOLS

Tod Schimelpfenig Curriculum Director – WMI of NOLS

Contrary to rumor, the eruptions we know as "sun bumps" have a real medical name - the polymorphous light eruption (PMLE).  Polymorphic light eruptions, the most common form of photosensitivity according to an article in the New England Journal of Medicine, are unusual reactions to light that, as far as can be determined, are not associated with other disease or drugs. 

Much of what we can read in the medical literature on PMLE is consistent with our experience.

As the name implies, these eruptions come in different forms, although an individual tends to have the same type of reaction.   Medically they are described as papules (a raised lesion on the skin) and papulovesicles (small blisters) that can coalesce into plaques and erythema multiforme–like lesions (red, pink raised rash).  Pictures in medical texts show that PMLE looks just like our sunbumps.  As we know, they can itch miserably, and sometimes have stinging sensations and pain.

Sunlight in general and UV-A specifically is thought of  as the causative factor in PMLE, although the overall natural history of the eruption is probably intertwined with skin type, diet, sun exposure, altitude, sensitizing cosmetics, sun cream use and other factors.  It's more common in people from northern climates and effects at least 10% of the population (21% in Sweden).  It's reported 3-4 times more in women than men.

We know PMLE can happen any time of the year but peaks in spring, possibly due to the increased reflection from snow.  The medical literature agrees.  Human skin adapts to UV exposure with time, known as the hardening phenomenon. This may explain the lower incidence of PMLE during the summer and fall.

The medical experts say that as little as thirty minutes of exposure can trigger the reaction, which will subside over 1-7 days without scarring.  Our experience is that it can take longer to resolve.

Prevention includes wearing protective clothing, using sun block and gradual exposure to the sun.  We know this does not work for everyone, and the medical literature agrees.  There are a variety of drugs that are used for people with recurrent reactions, none of which seen to be particularly effective.

Short term management treats symptoms, the prime one being itching.  Antihistamines and topical steroid creams are recommended, but really don't work all that well.  Unfortunately the reaction seems to run it's course despite our efforts to shorten the discomfort.

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