Regular grooming is the first step to preventing external parasites and skin disease. If your dog is longhaired, go over the coat on a daily basis with a blunt-toothed comb to remove foreign objects. Follow the combing with vigorous brushing in the direction of the coat. If your dog is shorthaired, rub down the coat with a short-bristled brush or grooming glove. Regular grooming not only helps keep your dog looking and feeling great, it provides an ideal opportunity for you to spot any signs of parasites or other skin problems.

Fleas
Fleas are the most common kind of external parasite. The animal infested is called the 'host', whilst the different species of flea are named after their most common host, for example the dog flea, cat flea, hedgehog flea and rabbit flea. But strangely enough, the most common flea found on both cats and dogs is Ctenocephalides felis - the cat flea. Dogs can also occasionally pick up fleas from rabbits, birds and hedgehogs.

The adult flea will feed on your dog and then return to the carpet to lay eggs, before starting the process all over again. Female fleas can lay up to 40 eggs every day, which are white, oval shaped and about half-a-millimetre long. Once laid, the eggs immediately fall off your pet into the carpet, among the floorboards or into bedding. Then, in between one and 10 days (depending on temperature and humidity; the average room provides ideal conditions) the eggs hatch into larvae, which pupate before the next adult generation is ready to jump back onto your dog. The adult flea feeds on blood and, when it bites, a small amount of its saliva penetrates the skin and may stimulate an allergic response in your dog. In fact, fleabite hypersensitivity is the most common cause of skin problems in dogs. If your dog is sensitive to the fleabite, a single flea can cause a lot of irritation.

How to tell if your dog has fleas
Fleas can be difficult to find as they move through the fur very quickly. A fine-toothed comb can help locate fast-moving adults - particularly in shorthaired breeds. But when you can't spot an adult flea, its 'dirt' (faeces) may be seen on the skin as small reddish black specks. Flea dirt can be differentiated from ordinary dirt by placing it on a moist white paper towel: whereas dirt will sit unchanged, the paper surrounding flea faeces soon reveals a reddish colour, which is actually blood in the faeces.

How to get rid of fleas
Contrary to general beliefs, natural products such as brewer's yeast, garlic, B vitamins, eucalyptus, tea tree oil and pennyroyal won't protect your dog against fleas. There is a vast array of flea products available in pumps, sprays, tablets, spot-on treatments etc. Some are only available from veterinary practices and may be necessary if the fleas on your dog have built up resistance to a commonly used product. Generally, you will need to combine a product that kills adult fleas (adulticide) with one that prevents the eggs and larvae developing into adults.

For best results, you should treat both your pet and your home. No matter how clean your home is, flea eggs can survive for long periods in carpets, cracks between the floorboards etc. If these are not dealt with, a new generation of adult fleas will soon develop. Vacuum frequently, discarding the vacuum cleaner bag after each use. If you are having on-going flea problems, check to see if you can place a flea collar in your vacuum cleaner - but remember to change it according to manufacturer's instructions as they lose potency after a while. Your dog's bedding should also be washed regularly.

Ticks
Ticks are bloodsuckers that bury their mouthparts under a dog's skin. Ticks are tiny - about the size of a pinhead, have eight legs, and can be black, brown, red or tan in colour. Once they attach themselves to your dog, they can swell up to the size of a grape.

How to tell if your dog has ticks
Ticks are just large enough to be visible, particularly when engorged with blood when they look like small warts. Just part your dog's fur and run your fingers along the skin.

How to get rid of ticks
Ticks can be removed but you have to be very careful that they don't leave their mouthparts behind in the skin or your dog may suffer a nasty reaction. Ask your vet to show you how to remove them, or use a flea product that works against ticks as well.

Lice
There are several kinds of lice, which are passed from pet to pet through direct contact. Blood-sucking lice, as their name suggests, feed on blood, whilst others chew the skin. Lice are small, dull and transparent, laying their eggs ('nits') on the hair shaft. These often show up well on a dark coat.

How to tell if your dog has lice
The most common sign of a louse infestation is a scruffy, dry hair coat. Loss of hair may occur and the dog may itch, sometimes very severely. Very heavy infestations of blood-sucking lice may occur, especially in puppies. You can normally tell that lice are present with the naked eye, with nits usually more visible than the actual louse, but often both can be seen.

How to get rid of lice
To prevent an infection, don't visit any dogs that you know to have lice. Check your dog regularly and, if you see anything suspect, go to the vet.

Ear mites
These parasites feed on the ear lining by piercing through the skin. Serum seeps from the wounds to make a characteristic brown deposit in the ear canal. In extreme cases, the eardrum may be pierced and permanent middle ear damage can result with such symptoms as loss of balance and convulsions.

How to tell if your dog has ear mites
Dogs that scratch or rub their ears may have ear mites. Regularly check the ears by gently wiping the inside with cotton wool on the end of your finger (never use a bud as the inside of a dog's ear is very delicate). Be very careful as it is very easy to damage the eardrum and, if you are at all unsure, get your vet to show you how to do it safely. If you see a brown discharge, your pet most likely has ear mites.