What are ticks?
Ticks are small, blood-sucking arthropods related to spiders, mites and scorpions. There are many different species of tick living in Britain, each preferring to feed on the blood of different animal hosts. If given the opportunity, some of them will feed on human blood too.
There are four stages of the life-cycle: egg, larva, nymph, and adult.
To the naked eye the larvae (with 6 legs) look like specks of soot, while nymphs are slightly larger, pinhead or poppy seed size. With their eight legs, nymphs and adult ticks resemble small spiders. It is the pinhead size nymph which is most likely to bite you.
Once a tick has started to feed, its body will become filled with blood. Adult females can swell to many times their original size. As their blood sacs fill they generally become lighter in colour and can reach the size of a small pea, generally grey in colour. Larvae, nymphs and adult males do not swell so much as they feed. If undisturbed, a tick will feed for around 5 to 7 days before letting go and dropping off.
There are several species of tick in the UK, but the one most likely to bite humans is the sheep tick, Ixodes ricinus. Despite its name, the sheep tick will feed from a wide variety of mammals and birds. The tick bite itself is usually painless and most people will only know they have been bitten if they happen to see a feeding tick attached to them.
See our detailed leaflet on ticks (PDF 223KB)
The Health Protection Agency website has some useful pages on ticks including a video and details of their tick recording scheme.
What diseases do ticks carry?
Three of the diseases that can be caught from a tick bite in Britain are
- Lyme borreliosis [bore-EL-ee-OH-sis]
- Babesiosis [bab-EE-see-OH-sis]
- Ehrlichiosis [air-LICK-ee-OH-sis]
Globally, the list of diseases is much longer.
Some ticks carry all three of the above diseases at the same time and can transfer them to you in a single bite. The resulting symptoms can be extremely confusing and liable to misdiagnosis. Treatment in such cases can be difficult.
See our leaflet on these diseases (PDF 255KB)
How big are they?
The tick that generally bites humans (the nymph stage) can be as small as a poppy seed or full stop on this page.
Small children are generally bitten above the waist—check their hairline and scalp.