Skin Disease


The itchy facts….

Skin disease affects thousands of dogs and cats every year, ranging from minor “hot spots” to extremely debilitating long-term skin problems. This is especially true in Hong Kong’s hot, humid summers but can occur at any time of year. As with all disease early diagnosis and treatment is essential. A positive fact is that many previously common conditions caused by fleas and mites are far rarer now due to the advent of great preventatives such as Frontline spray/spot-on® (fleas) and Revolution® (mites).

The following is a basic overview of common skin diseases seen in Hong Kong, divided into infectious, allergic and hormonal conditions. For further information please consult with your veterinary surgeon, alternatively contact the SPCA Veterinary Department on 28020501 or any of our branch clinics.

  • Infectious Disease
  • Allergic Skin Disease
  • Hormonal Conditions


Ringworm is the “general” name for the skin infection caused by a group of fungi (Microsporum spp. And Trichophyton mentagrophytes). The disease is more common in young, old, sick and immuno-compromised animals. The disease can be spread through the environment or direct contact, all it takes is skin contact with the spores. It should be noted ringworm is also infectious to people, but just as with animals, immuno-compromised people, such as HIV sufferers, people on chemotherapy and highly stressed people are more at risk. In general, if you do not have the disease by the time your pet is diagnosed then you are unlikely to get it.

The most common signs are broken and brittle hair, partial or patchy hair loss, scales and crusting, swollen or ruptured follicles, and areas of self-mutilation. Some forms of ringworm will glow under an ultra-violet light but many will not, definitely diagnosis usually involves taking a hair-pluck or coat brushing to culture the fungus which can take up to 10-12 days.

Treatment is needed for at least 1-2 months to ensure all the fungus has been removed from the skin and hair, and depending on the case it can involve oral anti-fungals, creams or shampoos. It is also important to treat the environment as spores can persist for long periods. All hard surfaces, bedding, rugs, cages and litter trays should be thoroughly cleaned/disinfected and carpets steam cleaned, if possible infected animals should be restricted to one room until negative to help reduce contamination.

For more information on Ringworm please download our information sheet.

Growth of ringworm fungus in culture medium. Note the redness of agar which indicates the presence of ringworm fungus.


Sarcoptic Mange

Sarcoptic mange is a skin disease caused by a mite (Sarcoptes scabiei) which is highly infectious. The mite lives in the superficial layer of the skin where it lays eggs, infected dogs will become very itchy and scratch and chew at their body, legs and head resulting in self-trauma, hair-loss and inflamed, crusting skin. Skin lesions are most commonly seen on the ear tips, elbows and hocks (and to a lesser degree on the abdomen and chest). The mite is not visible with the naked eye, so the disease is diagnosed by taking superficial scrapings of the skin and examining them under a microscope.

The good news is because the mite lives in the superficial skin layers it is relatively easy to kill. Various drugs including Revolution® can be used. As with all skin disease if there is secondary bacterial or fungal infection this must be treated too, and if dogs are very itchy a short course of corticosteroids may be given. In addition it is a good idea to treat the environment as the mite can live in bedding, brushes and blankets etc.

For more information on Sarcoptic Mange please download our information sheet.

Sarcoptes scabiei found in skin scrape under 40x magnification. A dog suffering from sarcoptic mange.

Demodectic Mange

This disease is caused by a mite (Demodex canis) which unlike the Sarcoptes mite lives deep in the hair follicles. An infected dog normally exhibits alopecia (hair-loss) around the eyes, face and forelimbs although in more generalised forms the hair-loss can be extensive. This disease is transmitted by direct contact, with puppies picking up the mites in the first 2-3 days of life from their mother. This disease is not contagious to other dogs, although a high proportion of normal dogs may carry a low number of mites on their skin.

Diagnosis is confirmed by microscopic examination of deep skin scrapings to visualise mites. There are various drugs available to treat this condition, but it should be noted treatment is often prolonged and at least two negative skin scrapings one month apart are needed to safely assume treatment has been successful. Unfortunately the disease can reoccur and can be particularly difficult to treat in Sharpeis, Dobermans and other short coated breeds. As transmission is from bitch to pups affected dogs should be desexed.

For more information on Demodectic Mange please download our information sheet.

Demodex canis found in skin scrape under 100x magnification. A dog suffering from demodectic mange.


Ear mites

Ear mite (Otodectes cyanotis) infections are especially common in puppies and kittens (but can occur at any age). Infection usually produces a characteristic dark waxy discharge and is intensely itchy for the animal involved causing them to shake their heads and scratch at their ears. In severe cases the canal can become completely obstructed by this “coffee ground” like debris. Whilst the mites cannot been seen easily with the naked eye, examination using an otoscope or microscopic examination of the debris will reveal the culprit mites!

Treatment involves ear cleaning to remove the debris, plus daily ear drops or Revolution® (applied every 2 weeks) to kill the mites. It is vital to get the ears checked by a veterinary surgeon after treatment has finished to ensure the infestation has been cured as stopping too soon can lead to relapse!

For more information on Ear Disease please download our information sheet.

Photo credit: Joel Mills

Otodectes cyanotis viewed under 100x magnification.

Regular ear cleaning is essential to the treatment of ear mite infection.


Allergies primarily result in itchy and inflamed skin. Your pet’s hair may fall out (or be chewed out) resulting in patches of alopecia, and their coat can become scabby, oily, scaly, dry or flaky. Allergic skin is also more susceptible to secondary infection from bacteria and/or yeasts. And as the skin inside the ear is the same as that covering the body, many allergic skin problems can result in otitis (ear inflammation and infection).

There are three main types of allergies:

  • Environmental
  • Food
  • Flea Bite Hypersensitivity

Unfortunately there is no easy cure for these conditions, and diagnosis involves a logical, systematic, and often slow, series of steps to rule out potential allergens. In addition treating other causes of skin disease, such as mites, fungus, bacterial infections and hormonal or behavioural disorders is vital before working up an allergy case.

For more information on Allergic Skin Disease please download our information sheet.


Flea Bite Hypersensitivity

A low level of fleas may not cause any obvious signs of disease in your pet. However allergic conditions can be caused by continual exposure to flea bite saliva, and increasing numbers of the parasite can lead to excessive scratching, depression, hair-loss and skin infections. Unlike mites fleas are visible with the naked eye on your pet, or their droppings can be seen on wet blotting paper from coat brushings.

Typical signs of skin disease include intense itching with hair-loss along the back and crusting of the skin. The good news is that with the advent of excellent preventatives such as Frontline spray/spot-on® and Advantix spot-on® this condition is rarely seen nowadays. But with so many products available it can be very confusing, so to find out the most suitable control regime for your dog or cat please consult your veterinary surgeon!

For more information on Flea Prevention please download our information sheet.


Photo credit: CDC

Photo credit: Dr Michael W. Dryden

A dog suffering from flea bite hypersensitivity.



Food Allergy

There are a large number of dietary items that can cause food hypersensitivity including beef, chicken, corn, cow’s milk, dairy products, eggs, fish, dog biscuits, lamb, mutton, pork, pasta, rice…to name but a few! Food allergies can occur in any animal, at any age, on any diet often one they have been eating for a long time. It is seen more frequently in younger dogs (less than 6 months old) and in cats from 4-5 years of age onwards. All areas of your pet can be affected although the head, ears and rump often get the worst of it. In a small number of cases, you might also see vomiting or diarrhoea. The only way a food allergy can be diagnosed effectively is via a dietary trial using a special hypoallergenic diet for at least 8 weeks. A Hypoallergenic Diet is designed specifically to reduce the risk of exposure to common food types, it is usually a protein source the animal has not been exposed to before e.g. duck or a “hydrolysed” protein. An improvement should be seen within 4-6 weeks but maximum improvement may take 10-12 weeks. After the dietary trial, your pet is slowly reintroduced to different foods from their old diet and observed for signs of itchiness and skin lesions, to find out what foods your pet can eat in the future. It requires patience but the information gained is invaluable in getting to the bottom of your pet’s skin problem.

Prescription diets designed to manage food sensitivity.



Environmental Allergies

And what about the environment? Again, a long list of potential culprits. Weeds, flowers, tree and grass pollens, moulds, dust mites, human skin and many others. Skin disease due to environmental substances (allergens) is called Atopic Dermatitis and typically develops in animals between 1-3 years of age. It has a genetic component so it is more common in some breeds with Chihuahuas, Yorkshire Terriers, Shih Tzus, Golden Retrievers, Labradors, Bull Dogs, West Highland White Terriers and Miniature Schnauzers topping the list! The allergens are absorbed across the skin so your pet can be exposed at any time. During the early stages of the disease itching is often the only symptom, commonly affecting the front feet but can progress to inflamed ears, axillae and inguinal areas (the back is rarely affected).

A technique known as Intra-Dermal Skin Testing is the best way to diagnose what your pet is allergic to. From the results of the tests a “vaccine” can be formulated using the offending allergens in an attempt to desensitise your pet (this treatment is called Immunotherapy). It may take up to a year to show signs of improvement, although many pets respond within 3-4 months. Immunotherapy is the only treatment available that can change the course of the disease, however, it involves a great deal of patience and the owner must learn to inject their pet. Other treatments include helping to control the disease by dampening down the immune response with either anti-histamines, corticosteroids or ciclosporin. Recently some new medicines and even a prescription diet have come on the market which whilst also not offering a cure can help reduce the symptoms of the disease and improve quality of life.

For more information on Allergen Specific Immunotherapy please download our information sheet.

Photo credit: JJ Harrison

Pollen grains on tulip anther.







Finally, a section on skin disease would not be complete without mentioning the affect hormones can have on the skin. The most common hormonal diseases causing skin problems include Hyperadrenocorticism (Cushing’s Disease) and Hypothyroidism both of which are common in older dogs. These diseases are normally diagnosed by clinical signs and blood tests and can be treated by adjusting the relevant hormones in the body (cortisol and thyroid hormone) using medications.

For more information on Canine Cushing’s Syndrome please download our information sheet.