Dermographism (skin writing): causes, triggers and treatment

Urticaria, or hives, is described by the British Association of Dermatologists (BAD) as a common illness affecting up to 1 in 5 people at some point, in which highly itchy raised weals come and go within hours. Most urticaria is spontaneous, but in inducible urticaria the weals are set off by a specific stimulus such as cold, pressure, friction or heat.

Symptomatic dermographism, or "skin writing", is the type triggered by friction. BAD says itchy weals occur after rubbing or stroking the skin, and weals and red marks often appear as lines at the sites of scratching, generally lasting less than an hour. The Primary Care Dermatology Society (PCDS) similarly describes weals triggered by rubbing or scratching and lasting generally less than an hour.

BAD notes that physical urticarias often occur in otherwise healthy young adults but can affect any age, and that some people have more than one type.

The main symptom is itch. The NHS describes hives as an itchy rash of raised bumps or patches that can sting or burn and may be pink or red on white skin, with colour harder to see on brown and black skin. In dermographism the pattern is distinctive: raised lines that follow the path of a scratch, waistband, strap or towel. Because scratching itself triggers more weals, itching can become self-perpetuating.

BAD says urticaria generally has no direct effect on general health, but it can have a high impact on quality of life, including mood, work and relationships. If the condition is affecting your mental health, PCDS advises discussing it with a health professional.

Urticaria is caused by the release of histamine and other chemicals from mast cells in the skin, BAD explains, and although it is often thought of as an allergy, it usually results from histamine release for other reasons. For inducible types the trigger is physical, and in dermographism it is friction or stroking.

The reason some people develop this heightened skin sensitivity is generally not found. BAD says some people with urticaria also have other conditions such as thyroid disease or other autoimmune disorders, and PCDS says a blood test is used to make sure there is no simple underlying cause such as an overactive thyroid when a person sees their GP about urticaria.

Medicines can aggravate or cause hives. BAD says almost any medicine can, but painkillers such as aspirin, ibuprofen and codeine, some antibiotics, blood products and vaccinations are the most likely, and asks people to tell their doctor if they suspect a medicine. If you suspect a medicine you can also report it through the MHRA Yellow Card scheme.

BAD says that usually the appearance, or a description of it, is enough for a doctor to make the diagnosis, that there is no special test that reliably identifies the cause of urticaria, and that routine allergy tests are not necessary. People who respond well to antihistamines do not usually need tests at all.

PCDS advises a GP appointment, with a blood test to look for an underlying cause such as thyroid overactivity, if you are worried about urticaria or it is not improving with the measures described.

BAD says antihistamine tablets block the effect of histamine, reducing itch and the rash in most people, though they may not relieve urticaria completely, and that if urticaria occurs frequently they should be taken regularly every day. PCDS stresses using non-sedating antihistamines rather than sedating ones, and says they can be taken for as long as the urticaria persists.

Both sources note that it has become common practice to increase the daily dose of non-sedating antihistamines up to four times the standard dose if needed, and BAD notes that even non-sedating types can occasionally cause sleepiness at higher doses. Changing the dose should be done on a clinician's advice. Antihistamines can be bought without a prescription, but PCDS says children are likely to need smaller doses and advice from a health professional, and that anyone pregnant should seek advice first. The NHS says a pharmacist can advise about antihistamine treatment, and that long-term conditions may affect whether they are suitable.

If standard antihistamines are not enough, BAD describes other medicines that specialists or GPs may add, such as a second type of antihistamine, montelukast, and, for the most severely affected people, treatments that suppress the immune system or omalizumab in specialist clinics, with oral steroids generally avoided because side effects usually outweigh benefits. PCDS says people whose urticaria does not improve significantly with an appropriate dose of a non-sedating antihistamine are usually referred to a dermatologist.

• Avoid aspirin, ibuprofen and other NSAIDs, and opiates such as codeine, unless essential, since BAD says they can aggravate urticaria.

• Avoid heat, tight clothing and alcohol if they worsen your symptoms; triggers vary between individuals.

• Because friction is the trigger in dermographism, scratching tends to bring up more weals, so try to avoid it.

• Keep a diary of when weals appear to spot patterns such as waistbands, straps or hot showers.

BAD says the aim of treatment of urticaria is to suppress symptoms until the condition improves naturally rather than to cure it, and that the course in any individual is unpredictable. For chronic spontaneous urticaria it quotes that in about half of people the rash lasts for 6 to 12 months before gradually disappearing, though it can last considerably longer; the sources do not give a separate figure for dermographism, so ask your clinician about your own likely course.

Other inducible types sometimes coexist. BAD lists cold urticaria, delayed pressure urticaria, cholinergic urticaria triggered by sweating, solar urticaria and aquagenic urticaria, and notes cold urticaria needs specialist assessment, including reporting it before operations so that you can be kept warm.

Dermographism itself is not usually dangerous, but hives can occasionally come with a serious allergic reaction. The NHS says to call 999 if lips, mouth, throat or tongue suddenly swell, breathing is very fast or difficult, the throat feels tight or swallowing is hard, skin or lips turn blue, grey or pale, or someone suddenly becomes very confused, drowsy or dizzy, or faints.

The NHS advises asking for an urgent GP appointment or calling NHS 111 if hives do not improve after 2 days, the rash is spreading, you also have a high temperature and feel unwell, hives keep coming back, or you have swelling under the skin (angioedema). Since dermographism is a recurring pattern, tell your GP rather than managing alone if it is persistent.

Most people are managed by their GP and pharmacist with antihistamines, with NHS dermatology referral for those who do not respond to appropriately dosed non-sedating antihistamines, as PCDS describes. Biologic treatments such as omalizumab are restricted to specialist clinics.

A private dermatologist can offer faster review and a structured plan if symptoms are disruptive. Tell any prescriber about all medicines you take and what has been tried, and avoid private allergy testing panels that are not indicated, given that BAD says routine allergy tests are not necessary.