At any one time 9% of the world's population are itching – here we define the common causes of and help you stop stratching
Itching is often contagious and overwhelming. You see someone else doing it and it’s hard to resist joining in, and just picturing lice crawling amid your hair or a tick wandering over your skin will make you want scratch. Many people feel the urge even if something ‘itchy’ simply comes up in conversation – I bet you’re feeling like having a good old scratch right now...
But what causes travellers to itch (besides the planning of our next trips)? And should we be worried about it?
Like pain, itching (or pruritis) alerts you to take evasive action or avoid a noxious stimulus – so that you’ll notice that tick or chikungunya-carrying mosquito and brush it aside before it bites and infects you. An itch might be useful for alerting you to the presence of a venomous spider or blood-hungry mosquito but once you’ve been bitten, the itch can drive you mad; it can make you tear holes in your own skin, which irritate further and create a route for infection.
Once you give in to the urge to scratch, of course, the need to excoriate only increases. Itching can thus be a destructive force, as anyone who has suffered a midge-attack or eczema flare-up can vouch.
Itching is an odd, incompletely understood phenomenon. It was thought to be a sensation similar to mild pain, although we know that painkillers are no help against it.
There are three possible mechanisms for itch. The easiest to understand is the kind experienced when you lie on or brush against some plant to which you are sensitive, or a biter or stinger injects its saliva or venom into you. Allergens such as ‘foreign’ plant or insect proteins trigger a response in the nerves supplying the skin, which release histamines that cause inflammation and itch. This reaction can be successfully treated with antihistamine tablets. Steroid creams can help too, because they also suppress the body’s inflammation reaction.
Other sources of itch are much more difficult to control. Itch can be due to disease; it can even be psychological. Indeed, there are tens of diseases that can cause pointless, sleep-wrecking, centrally-driven itching. Some itching may be driven by metabolic imbalance such as that caused by infective hepatitis (jaundice) or kidney failure; such whole-body disorders can also have you itching uncontrollably and miserably, yet the cause – being internal and wide-reaching – is extremely hard to treat.
At any one time it’s estimated that around 9% of the world’s population are itching. Women itch more than men and children more than adults. Skin that is hot itches more than cool skin (try rubbing ice on the affected area).
Fortunately travellers are most likely to be assailed by the more readily treatable causes of itch, and there are lots of approaches to treatment. Calamine lotion is an effective traditional itch-soother; white toothpaste is a useful alternative if you have nothing better. Steroid creams or ointments (eg hydrocortisone or Eumovate) are excellent for relieving itches caused by allergy or bites and stings, but can promote infection if the skin is broken by scratching – reduce the damage of scratching by cutting fingernails short.
Antihistamine tablets are far more effective in relieving itch than antihistamine cream; sedating antihistamine tablets can also be used to get a good night’s rest (but the best are only available on prescription).
Very dilute ammonia – After Bite is the most convenient form – stops some bites and stings itching. Half a teaspoonful of turmeric in half a glass of water is said to have some itch-relieving properties while certain herbs applied to the skin can be soothing – try chopped mint, basil, woundwort or Artemisia (wormwood) leaves. Some antidepressants and anticonvulsants appear to help treat centrally-driven itch, such as may be experienced by people on renal dialysis.
The most important strategy is to find a way of resisting the urge to scratch, or somehow distract yourself. This isn’t easy: when people are having a good scratch, levels of brain activity associated with bad feelings and unpleasant memories are suppressed, but there is increased cerebral activity in the area associated with compulsive behaviour. No wonder it is so satisfying.
Below we explain the cause of your itch, what it is, whether it is serious and how to treat it:
Insect bites or stings Raised, often itchy bumps emerge; No it is not serious, but it can mean exposure to disease; Use antihistamines or steroid creams.
Infestations (eg lice and fleas) Caused by insects that feed on blood; No, but occasionally carry disease risk; Put bedding and clothes out in direct sunlight and apply malathion or pyrethroid.
Dry skin Flaky and tight skin; No; Moisturise.
Fungal infections and athletes foot Flaky and itchy patches; No; Best is Terbinafine (Lamisil) cream.
Scrapes and scabs The normal healing process – time; No; Scabs often become itchy as they heal.
Allergic reactions Raised, itchy, flaky red areas of skin; Rarely; Antihistamines.
Hives (aka urticaria) Short-lived, raised, itchy wheals; No; Antihistamines.
‘Hairy’ plants or furry caterpillars Hairs penetrate the skin and irritate; No; Remove the hairs with pointed tweezers.
Eczema From mild itching to severe inflammation; Rarely if properly treated; Moisturisers and steroid ointments.
Scabies Excruciating itching; worse at night; No but it is distressing; Apply permethrin or malathion to whole body.
Loa-loa worm Caused by microscopic filarial worms spread by horse-flies in Africa; Never life-threatening; See a doctor.
Liver and kidney disease In severe disease waste products cause itching; Yes; See a doctor.
Anaemia Lack of iron due to eating too little or losing too much blood; Rarely; Take more iron – over the counter iron supplements are usually insufficient.
Geography worm Under the skin worm; No; Get a doctor to freeze its head.
Onchocerciasis (river blindness) Itching usually confined to one limb and caused by microscopic filarial - worms spread by black-flies in Africa; Rarely; See a doctor.
Schistosomiasis (bilharzia) Caused by worms that penetrate the skin during swimming and paddling; Rarely if left untreated; See a doctor – and arrange blood tests after treatment.
Jellyfish stings Itching can persist weeks and even months after a sting; Usually it's not serious, but globally five species are dangerous; Remove any stinger from the skin and apply steroid ointment
Dr Jane Wilson-Howarth is not good at resisting the itch so she works hard on avoiding bites.
For more articles by Dr Jane Howarth-Wilson...
