Sun Allergy

Dr. Sarkany is the Head of Photodermatology (sometimes called ‘Photobiology’) at St. John’s Institute of Dermatology in London. He also works at the Lister Hospital (Chelsea, London), and Shirley Oaks and North Downs Hospitals in Surrey.

Dr Sarkany By Dr. Robert Sarkany, FRCP MD, Consultant Dermatologist and Photodermatologist, London

A guide for people suffering from unpleasant skin reactions to the sun and to sunlight.

Many people suffer from unpleasant and uncomfortable skin reactions to sunlight.

There are, in fact, several different diseases, with different causes and treatments, which can cause reactions to sunlight.

The details of each light sensitivity disease are outlined below, but if you have a skin problem with sunlight, the key is to find the cause i.e. to diagnose which type of sun sensitivity you have.

Clues from the timing of your sun allergy reaction

How can my sunlight allergy be diagnosed and treated?

The Main Types Of Sun Sensitivity

• Polymorphic Light Eruption
• Light sensitive eczema.
• Solar urticaria
• Erythropoietic Protoporphyria
• Medication-Induced Photosensitivity
• Actinic Prurigo
• Xeroderma Pigmentosum (XP)

The first thing is to know how long after the sun exposure it takes for your problem to begin:

Clues from the timing of your sun allergy reaction

• If you have attacks of pain or itch immediately on sun exposure (within seconds or minutes) the most common causes of this type of reaction are:Medication- Induced Light Sensitivity, Erythropoietic Protoporphyria and Solar Urticaria.
• If you have an itchy rash that comes up a few hours after sun exposure and lasts a few days, the most common cause is Polymorphic Light Eruption.There are many rarer causes, all causing slightly different types of problems, including light-sensitive eczema, lupus and actinic prurigo.

Diagnosis and Treatment

How can my sunlight allergy be diagnosed and treated?

For the doctor, the first task is to diagnose the cause of the light sensitivity since treatments for the different diseases are completely different. Also the type ("wavelength") of light causing the problem is different in the different diseases, so a sunscreen which is useful in one disease may not be useful in another disease.

The medical specialty dealing with skin reactions to sunlight is called Photodermatology. It is a branch of Dermatology. In recent years, there have been advances in the understanding and the treatment of sunlight-induced skin problems.

What can your Dermatologist do for your sun allergy problem?

Working out the cause of the sun allergy depends a lot on what a patient tells the Doctor. For one thing, your rash (if you have one) may have disappeared by the time you are seen, so there is nothing to see any more.

What can be discovered during the Consultation: As well as the description of the attack (how the skin feels during an attack, which places are affected and what the rash looks like if there was one to see), the timing of the rash is crucial because timing distinguishes many of these diseases from each other. Did the rash take minutes or hours to come on after going out in the sun, and how long did it take to then go away? Once you have been assessed by your Dermatologist in the clinic, tests can be arranged.

Tests for patients with sun sensitivity: The tests done depend entirely on what has come out of the consultation. There are specialised blood tests (e.g. porphyrins, HLA typing, lupus serology) . there are also “light tests”. "Phototesting" involves using machines, particularly the "monochromator”, to test the reaction of skin to different types of light especially the various wavelengths of ultraviolet light. It is useful in some, but not all, types of sunlight allergy (especially chronic actinic dermatitis and solar urticaria). Phototesting is a specialized test requiring special equipment and expert technicians, and is not available everywhere, but there are some centres in the UK that provide it.
Treatment: Treatment depends not only on the diagnosis of the cause of the light sensitivity (see below for details) but also from finding which type of light is causing the problem so one can use sunblocks, and sometimes window film filters, to block out the wavelengths of light causing the problem.

The Main Types of Sun Sensitivity:

• Polymorphic Light Eruption
• Light Sensitive Eczema.
• Solar Urticaria
• Erythropoietic Protoporphyria
• Medication-Induced Photosensitivity
• Actinic Prurigo
• Xeroderma Pigmentosum (XP)

This is the commonest cause of sunlight reactions. In its mild form it is often described as ‘prickly heat’ by patients, but it can be more severe and persistent. It causes itchy red bumps, which often join together, to come up usually a few hours after sun exposure. It can affect any area of skin exposed to sunlight, though in m any sufferers some areas of skin get the rash whilst others may be more resistant. It often causes problems only on hot holidays, tending to last for up to a week or so after one returns home. Some patients have the problem in the UK often throughout the Spring and summer, usually from around Easter until September or so. It is common, affecting to some extent around one in six young women , and can start at any age in men or women. The ‘allergic’ skin reaction to the sunlight is to the ultraviolet part of the sunlight. There are two types of ultraviolet in sunlight , A (UVA) and B (UVB). In most patients, the rash is triggered by UVA so, for many people, the only sunscreens that work are 4 or 5 star UVA protective sunscreens (the SPF (sun protection factor) only tells you about protection against UVB). In severe cases, treatments include oral steroids and ultraviolet desensitisation therapy: the choice of treatment depends on the exact features of the rash in an individual.

In many people with the common type of eczema (‘atopic eczema’) that is particularly common in children, the eczema flares up in sunny weather. Sometimes this is because of humidity, heat and sweating, but in many people it is a direct worsening of the eczema caused by ultraviolet in sunlight. This is called ‘photoaggravated eczema’. A broad spectrum (i.e. UVA and UVB) sunscreen can help to reduce these flares in some patients. The flare of eczema is treated with the same ointments and creams as the ones used for non-sunlight related eczema.

There is a rarer type of sun-induced eczema where the skin is terribly sensitive to sunlight which causes severe eczema. This is called ‘chronic actinic dermatitis’. It most often begins in middle or old age. The eczema is very severe in some patients. It quite often does persist during the winter, but it may be very severe in the spring and summer with severe and often rather thick and itchy patches of eczema especially on the face and hands. The allergy is to ultraviolet in sunlight, usually UVB. The severity of the sunlight sensitivity means that sun protection with high factor sunscreens and sun avoidance are very important, but even with these measures the eczema can be difficult to control with ointments and creams and some patients need treatment with drugs that suppress the immune system to control the eczema. The test used to confirm that this is the diagnosis is Monochromator Phototesting. Many patients also develop allergies to various substances their skin encounters in the environment as well.

This causes a reaction within a few seconds or minutes of exposure to sunlight, of urticaria (or ‘hives’) ----itchy swollen often red patches. The reaction settles down within a few minutes or generally an hour or two once one gets out of the sun. Some patients do get this condition very badly, sometimes winter and summer, and it can be disabling. Phototesting is needed to confirm the diagnosis and find out which types of light are causing the reaction. An extra complication is that, unlike most light sensitive skin diseases which are caused by ultraviolet light, solar urticaria is often caused by ultraviolet but can be caused by visible non-ultraviolet light, for which conventional sunblocks will not be effective. Antihistamines sometimes in high dose , help many patients, and a variety of other treatments can be helpful. Because of potential treatment complications, this condition is generally only treated in specialist centres with experience of patients with this disease.

A rare genetic disease which causes problems from childhood onwards. Most patients have started having problems by the age of four years. Exposure to spring or summer sun causes a burning pain, especially on the banks of the hands, tops of the feet and face, which often last for two to three days, usually with nothing more to see them a bit of mild swelling. Standard painkiller tablets don't usually help but cold air or cold water can relieve the pain a little. Although it is genetic, in many families no one else in the family may have suffered from it previously. Although no treatments are totally effective for the painful attacks, beta carotene and hospital ultraviolet light therapy may help some sufferers. Since the pain is caused by visible light, commercially available sunscreens do not help, but a hospital-prescribed visible light sunscreen can be useful, as can window filter films. Blood tests need checking once a year to check that the very rare liver complications are not occurring.

Some medications, particularly doxycycline, some nonsteroidal anti-inflammatory drugs, thiazides and amiodarone, can cause sun sensitivity, most often pain, redness and swelling within a few seconds or minutes of sun exposure lasting a few hours. Less often there is a longer lasting rash on exposed areas of skin. The problem generally settles down within a few days of stopping the medication though occasionally it can take up to three months to go away.

This is quite a rare condition in which itchy bumps occur mainly on exposed skin, which can persist for many months and can leave scars when they disappear. It is commoner in children. Sometimes patients or their relatives may have polymorphic light eruption too (see above for details). Treatments include broad spectrum sunscreens, steroid creams and , in severe cases, tablets such as prednisolone or thalidomide. Sometimes hospital ultraviolet light treatment can help.

A very rare genetic skin disease, important to diagnose early because failure to protect against light in early childhood can increase the chance of a child developing skin cancer later. In many patients it causes severe sunburn reactions which occur even when the sun to which the child has been exposed is not that strong. The dermatologist will also look for an unusual type of freckling pattern on exposed skin. It is diagnosed by a test which involves having a skin biopsy (i.e. a small piece of skin cut out). It can also cause eye problems and problems in the brain in a few patients.