How can I avoid mosquito bites?

In certain parts of the world mosquitoes can infect you with malaria, dengue fever or West Nile Virus, so you need to check what preventative drugs or vaccinations you need. In other places you just need to worry about reacting to the saliva they leave in your skin when they snack on your blood. It's the saliva that prompts your immune system into making the skin around the bite swell, redden and itch. Mosquitoes like some people more than others (those with blood group O are popular) but make yourself unattractive by using a repellent with DEET (apply to skin and clothes). You need it in up to 35% concentration – but children should have no more than 10% applied to them. Oil of lemon eucalyptus should not be used on children under three years of age, although it does work (but not as well as DEET).

How can I treat mosquito bites?

Don't scratch – the bite will itch more and could get infected. Wash it with soap and water. You can use an over- the-counter steroid ointment (1%) to reduce any reaction and if you have many bites you may need an antihistamine tablet. It's rare to get an acute allergic reaction (throat swelling, difficulty breathing and chest pain) but if this happens seek emergency attention.

What about gnats?

They can also bite ferociously and, like mosquitoes, hang around near water and attack mostly in the evenings. The measures against mosquitoes also work for gnats. They love ankles, so wear long socks.

What should I do about jellyfish?

Jellyfish have tentacles that contain little bulbs (nematocysts) which release stingers (small injections of poison) when they touch prey or human skin. Wet suits offer protection. Don't pick up jellyfish on the beach as they still have their stingers. Do not rub an area of skin where you've been stung as it makes it worse. Wash off the stingers as soon as possible using sea water. Do not use tap water or drinking water or cold compresses. You may also need to pick off any tentacles with tweezers. Then soak the area in vinegar (don't use vinegar for Portuguese Man O'War jellyfish) for up to half an hour. Deactivate any poisonous bulbs left in the skin by applying shaving foam, or baking powder and sea water as a paste, and scraping it away when the foam or paste dries with a credit card. If someone has a severe allergic reaction (widespread rash, chest pain, high temperature or difficulty breathing) they need emergency treatment.