Not all ticks carry pathogens, so a tick bite does not automatically mean you will get sick. Ticks spread a variety of diseases, the most serious of which for humans, if left untreated, are Lyme disease and tick-borne encephalitis. Lyme disease is much more common and is treated with antibiotics. There is no drug treatment for tick-borne encephalitis, but a vaccine is an effective way to prevent its transmission.

A tick stuck to the skin usually stands out as a dark spot, which may initially look like a mole. Small, adolescent nymphs can be very difficult to spot due to their small size of 1–2mm. A bite which the tick has already left is more challenging to detect, as the skin may not show anything abnormal. It is therefore a good idea to check for ticks immediately after going outdoors, so that they do not have time to attach to the skin for a long time and can be detected before they fall off. Take particular care to examine at least the armpits, groin, earlobes, scalp, back, abdomen and backs of the knees.

A tick can be removed by pulling it out of the skin in a smooth upward motion. The easiest way to do this is to use tick tweezers or normal tweezers, available from the pharmacy, to get as close to the surface of the skin as possible. Grease or insecticide should not be used to try to remove a tick. If the tick can be removed from the skin within 24 hours, the risk of Lyme disease infection is low.

The bite should be monitored for a few weeks. Almost everyone will get a patch of redness 2–3cm in diameter at the bite site as a reaction to irritation, but this does not yet indicate a Lyme disease infection and does not need to be treated. If the bite develops into an enlarged patch of redness of more than 5cm in diameter after a week or two, an infection caused by the Lyme bacterium is likely and should be treated with antibiotics. Even at this stage, there is no need to visit the emergency department. It is sufficient if you go and see a doctor within a few days. Another, much less common skin symptom of Lyme disease is a bluish, unscarred, smooth, soft nodule, most commonly found on the earlobe, scrotum or nipple.

Tick-borne encephalitis is an infectious disease caused by a virus. If a tick carries this virus, the disease can be transmitted within minutes of its initial bite. The first symptoms are fever, headache and joint pain about a week after the bite. This usually lasts 4–7 days. Most people are completely cured at this stage and gain lifelong immunity to the disease. In some people, the disease progresses to a second stage, preceded by a period of 3–21 days without symptoms or with just mild symptoms. The symptoms of the second stage are severe and require immediate treatment. These include high fever combined with headache, stiff neck, sensitivity to light, and nausea. The sufferer may also experience loss of consciousness, seizures and paralysis. Tick-borne encephalitis is diagnosed by symptoms and antibody tests, and is treated symptomatically. Antibodies cannot be detected until 1–2 weeks after infection at the earliest, so testing for antibodies immediately after a tick bite just to be on the safe side is unnecessary.

When outdoors, you should try to guard against ticks by wearing protective clothing. A tick repellent that can be applied to the skin is also available from the pharmacy. Check your clothes and skin after being outdoors. You should also check the fur of your pets, as they can carry ticks indoors. Tick-borne encephalitis can be prevented with the TBE vaccine, which is particularly recommended for people living in high-risk areas and those who spend a lot of time outdoors. There is currently no vaccine available to prevent Lyme disease.