Dr's Casebook: Dr Keith Souter: Beware of the midges on your holiday

Biting midges are found all over the world. They have been an incredibly successful life form, and have been biting other creatures for a staggering length of time. They have actually been found in 120 million year old pieces of amber. They are incredibly small, an adult insect’s wingspan measuring about 1.4 millimetres. They weight a measly 0.5 micrograms, but they can inflict a great deal of pain.

The problem is that they swarm in potentially huge numbers. There is an old saying that you swat and kill one midge and a hundred will turn up to its funeral. If you have been caught by them then you will know the truth of the saying.

In the UK we have about 37 species midges in the genus Culicoides, of which the most vicious of them all is Culicoides impunctatus. It is the one responsible for 90 per cent of attacks on humans. The midge season lasts from mid-May until September.

The female of the species is the biter. After mating they need a blood meal for the eggs to develop. Warm-blooded mammals are the prime targets. They are attracted to dark-coloured moving objects, especially when they give off carbon dioxide. In other words, mammals breath! They also are attracted to chemicals in perspiration. And research has shown that they do prefer some people’s sweat more than others

When a female midge lands on your skin it cuts out an area of skin and starts to suck the blood. Then as she feeds she releases chemicals called pheromones which attract other females and a mass attack begins.

If you are going into midge territory this summer I would advise two things. Firstly, get some Avon’s Skin So Soft spray. Apply it liberally. Secondly, carry a small tube of toothpaste with you and apply a dab on any bite. It will sooth it and prevent it bruising and itching.

I will be carrying both on our walk. And I confess, I'll also have a mosquito mask when out on the moors.