In this three-part series we first delve into how the skin works, what the signs of healthy skin are, and how it is susceptible to problems; next month we'll bring you a practical guide on things you can do to ensure your pet's skin remains healthy; and finally we'll look in more detail at certain skin complaints and how they are treated.
How skin works
The role of the skin is to provide a protective outer layer, regulate body temperature, and give a sense of touch. The skin is split into three layers:
- EPIDERMIS: This is the thin but tough outer layer. It contains cells which produce melanin, the pigment that gives the skin its colour and protects it from ultra violet radiation.
- DERMIS: The thick layer which nourishes the epidermis and contains nerve endings, sweat glands, hair follicles, blood vessels, and sebaceous glands, which secrete oil on to the hair follicles, keeping the skin moist and helping build a barrier against foreign bodies.
- SUBCUTANEOUS LAYER: A layer of fat which contains many different functional cells, providing insulation from the hot and cold and storing energy.
As well as protecting against foreign bodies, the skin keeps in vital fl uids and nutrients. The outer layer of the skin is constantly shedding and replacing itself with new cells. The rate at which cells are replaced is affected by nutrition, hormones, illness, and genetics.
Signs of healthy skin
When inspecting your pet there are several things to look for that show his skin is in good condition.
- Healthy skin should be supple, clear, and consistent in colour. The skin should not be flaky, greasy, or have a thickened appearance and texture. Allowing for breed differences, a dog's coat should be full, shiny, and pliable, not brittle or broken.
- Grooming your dog correctly will help stop his coat and skin being damaged. In particular, taking care not to over-bathe him will ensure his natural oils are not destroyed. Nutrition also plays a key part in skin. Feeding a balanced, healthy diet, which includes all the correct nutrients, will help to nourish the skin and keep it moist.
- Most of the time your dog's skin does a great job but being a complex organ it is susceptible to a variety of problems. Itching and poor skin health are often the first symptoms of a problem.
"The canine skin is badly designed compared to human skin," explained Susan Paterson a european specialist in veterinary dermatology. "In humans the skin grips each hair closely. Dogs have compound follicles which means there are lots of hairs coming out of each single gap, which leaves space for infections to get in."
Skin problems often fall into three main categories. The symptoms though are similar. Excessive scratching or licking, flaky skin, or signs of irritation can indicate a problem. Understanding skin problems can help to get to the bottom of what is causing them. Over the page we look at the types of problem and how to spot them.
Sometimes substances that are usually harmless trigger a reaction in a dog's immune system, which treats them as foreign bodies. This hypersensitivity is an allergy.
There are different types of allergy depending on how a dog encounters the substance which causes the reaction - known as an allergen.
- INHALANT ALLERGIES - this is where the allergen is something that is airborne and can be inhaled, such as dust, mould, and pollens.
- CONTACT ALLERGIES - the least common allergies in dogs. This is where a dog's skin reacts to something it comes into contact with. These often include disinfectants, pesticides, and materials such as wool or synthetics found in bedding and clothing.
- FOOD ALLERGIES - dogs can be allergic to certain foods. The most common food allergies in dogs are to beef, milk, and wheat.
When an allergen is detected chemicals called histamines are released which initiate the allergic response. In humans, histamines are released mainly in the respiratory system, which is why an allergy in a human will often cause them to sneeze, or have a stuffy nose, or watery eyes. In dogs, on the other hand, histamines are mostly found in the skin. This is why, although dogs with allergies may show signs of sneezing or runny eyes, the symptoms are predominantly skin problems.
With various treatments, including changes to diet, oil supplements, and medication including antihistamines, allergies can often be kept under control. "I would hope an allergic dog is 90 per cent comfortable, 90 per cent of the time," said dermatology specialist Susan Paterson.
By far the most common cause of skin complaints are parasites, and fleas in particular. While the presence of fleas is enough to make a dog itchy, many dogs suffer far more from an allergic reaction to flea saliva. When the parasites suck blood from a dog they inject it with a special saliva that keeps the blood flowing. This is highly irritating to some pets and causes them to itch all over - not just at the site of the fleas.
Other parasites can cause skin irritation too. Ticks are tiny arachnids that gorge on blood. As well as carrying diseases such as Lyme disease, a bite from a tick can cause inflammation of the skin, infections, and irritation, as well as more serious symptoms.
Various forms of mites will also try to make themselves at home in your dog's coat and skin. Sarcoptic and demodex mites can cause mange, a skin disease that can lead to severe itchiness, hair loss, scabs, and a thickening of the skin.
Other mites include harvest mites, which can cause severe itchiness, and cheyletiella mites, which only occasionally cause severe itchiness in dogs but do make the skin flaky, crusty, and scabby.
Dogs can also be infested with lice resulting in itchiness, hair loss, and a dry, scruffy looking coat. However, unlike in humans, lice are rare in dogs.
A rarer form of skin problems in dogs is autoimmune diseases. As in humans, a dog has an immune system to protect the body from foreign bodies which can cause disease and infection. For reasons which are still not fully understood, immune cells can sometimes mistake healthy cells for foreign cells and try to destroy them. In effect, the body attacks itself.
There are a several autoimmune skin diseases. The most common is pemphigus which has four varieties: pemphigus foliaceus, pemphigus erythematosus, pemphigus vulgaris, and pemphigus vegetans. They differ in their severity and slightly in their symptoms, although the main signs are ulcers, crusting of the skin, redness of the skin, and pus-filled sacs.
Other forms of autoimmune skin diseases can affect dogs, including discoid lupus erythematosus (DLE) commonly known as collie nose. Dogs will often lose pigmentation around the nose.
With ongoing treatment, these conditions can often be managed and brought under control.
One of the things that makes skin ailments difficult is that affected dogs often get secondary problems such as infections.
Poorly pets will often damage the outer layers of skin with incessant scratching, or the original problem may have caused a weakness that makes it easier for infections to infiltrate the body.
Bacterial infections, known as pyoderma, aggravate existing symptoms and can cause itchiness, loss of hair, crusty skin, pus-filled swellings, and lesions. Dogs can also get abscesses, which usually contain pus, and moist eczema, a large raw moist swelling more commonly known as a hot spot.
Dogs with underlying skin problems are also more prone to yeast infections. These fungal infections can be extremely itchy, cause skin to thicken, and give off a distinctive odour.
Ringworm - despite its name - is another fungal infection. This fungus feeds on keratin, the fibrous proteins which help make up the outer layer of the skin. Patches of hair are lost but sufferers are not usually itchy.
As well as treatment for any underlying problem, antibiotics and antibacterial shampoos are commonly used to help cure the infection itself.
In healthy dogs, the sebaceous glands are joined to hair follicles in the epidermis layer of the skin. The glands secrete sebum, the natural oil which keeps the skin healthy and moist, and which also gives the hair its sheen and has antibiotic qualities. An underlying skin problem can cause the onset of seborrhea, a condition where the glands release too much oil. This causes the skin to be flaky and greasy and gives it a smelly odour. Once the underlying problem is under control the disease usually disappears. However, primary seborrhea, which is not caused by any problem, is an incurable condition.
Solving a skin problem
If your pet has a skin problem then a trip to the vet is almost inevitable. However, there is a lot owners can do to help ease any skin complaints.
"Before you go to the vet, make sure your dog has decent flea control," explained dermatology specialist Susan. "Not only are fleas a common allergy they also make other skin diseases worse as they stir up the whole immune system.
"If your dog is itchy also look at his food. Try a diet that is cereal free, red meat free, and dairy free. Make sure you actually look at the ingredients on the packet.
"There are also supplements such as salmon oil and flaxseed oil you can try. Often this will soothe a problem and if you still need to go to the vet's you have already ticked several boxes."
Skin complaints can often take some detective work to get to the bottom of the problem. Your vet will need your dog's medical history and diet, and further tests may be needed.
Helping your dog overcome a skin complaint can take perseverance. Ensuring a disciplined approach to treatments and tests is important. It is usually well worth it though as the prognosis in many cases is good. "Many dogs make good progress, to the extent that people would never know their dog had a skin problem," said Susan.