When to check if that itch is hives
Hives are known in the medical world as ‘‘urticaria’’, a name derived from the British stinging nettle plant Urtica Dioica.
Anyone who has ever been stung by this particular plant will know instantly what I’m talking about but if you haven’t, the rash seen in hives is classically bumpy, red or pale coloured and appears quickly.
The skin around the bumpy or raised bits is typically red, and sometimes, depending on the part of the body affected, there can also be significant swelling of the underlying tissues.
Hives are itchy, look quite dramatic and can cause considerable distress, but the good news is that they aren’t dangerous (though occasionally the underlying cause can lead to more serious issues).
If it comes on quickly and disappears within a few days (very occasionally up to six weeks) it is known as acute urticaria. If it lasts longer, it is termed ‘‘chronic’’ urticaria.
Around one in six of us will get acute urticaria at some point and a much smaller proportion (1 in 1000) will suffer from the longer-term version. We know that people who are ‘‘atopic’’ – people who suffer from allergic conditions including eczema, hayfever and asthma – are more likely to suffer from urticaria.
At a cellular level, urticaria is caused by the release of histamine and other chemicals from mast cells in the skin.
These chemicals cause leakage from tiny blood vessels known as capillaries, which leads to the typical swelling and redness. There is usually a ‘‘trigger’’ that activates the mast cells, but often this can’t be identified.
Triggers include physical contact with irritants such as plants (as the names suggests), chemicals, latex or rubber. In these situations, classically the rash will appear only in the area where the contact occurred, rather than spread all over the body.
Other triggers that can cause more widespread hives include:
■ Certain foods (shellfish or strawberries), insect bites and stings and medication. These substances can all cause allergic reactions and although many people will just get the rash of hives, others can be affected far more seriously with compromised breathing and circulation known as anaphylaxis.
■ Viral infections.
■ Physical stimuli, including extremes of temperature – hot and cold – and exposure to sunlight. This type of urticaria can be dramatic, as
Many people will just get the rash of hives, but others can be affected more seriously with compromised breathing and circulation.
the rash appears rapidly and can spread all over the body (someone I knew used to pull it out as a bit of a party trick, diving into a cold lake, then coming out red and swollen). It can also be caused by pressure or rubbing on the skin. People will often describe something known as dermatographism, where the rash appears in exactly the spot they have just scratched or pressed.
■ Stress.
■ Exercise.
Many of these types of urticaria will only happen once in someone’s life, but some will get recurrent bouts and will never grow out of it. To diagnose urticaria, your doctor will usually just need to look at the rash. However, as it often disappears leaving no trace at all within a few hours, take some good photos, as there may well be nothing to see by the time you get to your appointment.
Occasionally, if there is any uncertainty about what is going on, you are unwell or have any unusual symptoms, your GP might suggest further testing, either with bloods or a referral to a dermatologist but most of the time this won’t be required.
If you get urticaria, the first thing to do is to try to identify a trigger. Think about what you have eaten, any medicines you might be on, and anything physical that could have precipitated it (for example, exercise, temperature change or exposure to water or sunlight).
You may not be able to make a connection, but if you do, avoiding that trigger will reduce your risk of getting urticaria again.
Your doctor will suggest antihistamine tablets, as they will block the production of histamine from the mast cells, reducing the rash, itch and swelling. Sometimes they will advise taking these pills more frequently than is usually recommended, depending on the severity of your symptoms.
In most cases, this will be all that is needed to settle things, though in rare situations other medication can be required, especially if you are unlucky enough to get the ‘‘chronic’’ type.