Hair loss that occurs on the top of the dog and forms a triangle of hair loss, with the widest part of the triangle at the base of the tail and the point somewhere between the base of the tail and the shoulder blades, is usually due to flea bite or mosquito bite hypersensitivity.

There are some conditions that can resemble flea allergy, including hypersensitivity to anal sac secretions, food allergy and sometimes inhalant allergies. Almost all allergic conditions respond to treatment.  

There are also times when the hair loss occurs due to hormonal disease. These disorders are more common in older dogs, usually six years of age or older. Hypothyroidism is the most common hormonal disorder leading to skin problems so it made sense to check for that first.

The next most common problem is hyperadrenocorticism (Cushing's disease, HAC).  This is a disorder in which high natural cortisol levels are causing hair loss and skin irritation.

If your vet is unable to resolve the problem after several visits, it might be a good idea to ask for referral to a veterinary dermatologist.  Most of the time, if you work with your vet and you both are patient, skin problems can be resolved.

Other skin issues can be seasonal flank alopecia or hormonal disease. There is a condition, known as "seasonal flank alopecia" which occurs in some breeds. This condition usually is seasonal and occurs in some dogs during the colder months and other dogs during the warmer months. It should clear up at least part of the year. There is hair loss on the flanks and the skin does get darker. The usual recommendation is not to treat this condition the first time it occurs because sometimes it doesn't come back. If it does come back the next time the season that is associated with it rolls around, then it might be worth trying melatonin.

The other thing to consider is other hormonal disease. Hyperadrenocortism is a fairly common cause of hair loss and increased skin pigmentation and there are other hormonal disorders that can cause similar signs. It seems reasonable to me to try to rule out this condition prior to looking for one that is more rare. Your vet may have already done this or may have good reason not to consider hyperadrenocorticism but it would be worth asking about it.

Hair loss - Cushing's disease.
This condition is not very common. It is possible to diagnose hypothyroidism more accurately at this time than it was possible in the past few years. The free T4 level measured by equilibrium dialysis, especially when combined with a TSH level test, is pretty accurate at determining if hypothyroidism is present. It is possible that your dog does have this problem. Cushing's disease can occur without many of the normal symptoms.   Testing for Cushing's disease (hyperadrenocorticism) is usually done by low dose dexamethasone response testing, in which a blood test for cortisol is drawn around 8 AM and then an injection of dexamethasone is given. Cortisol samples are taken again at 6 hrs and 8 hrs after the injection. If a dog has Cushing's disease the cortisol levels are not suppressed by the injection. There are other tests for this condition.

It is possible that allergies or an infectious agent such as ringworm could cause hair loss in a small spot, but I would expect it to spread from that point -- especially with allergies. A contact allergy might result in a spot similar to the one you describe.  

Some dogs develop areas of hair loss over vaccination sites.  I have seen this problem and the skin appeared irritated and thickened at the site in addition to the hair loss. I think that a skin biopsy could be very informative if the problem persists. You might want to discuss this option with your vet.

Almost all other causes of hair loss in dogs should be considered, so it is important to eliminate mites, anal sac irritation, flea allergy, flea infestation, etc. I'm sure your vet has probably been eliminating those problems as in examining her. If you wish to have a second opinion from a specialist, there are veterinary dermatologists and your vet can probably arrange to refer you to one.

Bilaterally symmetric hair loss :  Bilaterally symmetric hair loss without itching is indicative of hormonal disease, such as hypothyroidism or Cushing's disease. When itching is present it is necessary to consider the hormonal diseases and other conditions that can cause hair loss such as allergies and flea infestation.

Owners of young dogs affected with allergies should strongly consider trying hypo sensitization ( injections of small amounts of the substances causing allergies to make the dog's body less reactive to them). This does not work for all dogs but it is a much better approach than using corticosteroids to control the itching, when it does work. If going to a dermatologist isn't possible your vet can do the basic testing to ensure that problems like demodectic mange, sarcoptic mange, skin infections and immune mediated disease are not present and then provide medications that will help with the itching. It is imperative to change your food source to a human grade more basic food such as duck and potato or fish and potato etc.  Food is known to be a major cause of canine allergies.

Also look into any environmental triggers, such as carpets, cleaners etc.
  
If your pet is suffering from a topical skin problem or you have been told your pet has allergies. Please read... Instructions for Yeast Problems:

The following serves as an introduction to skin diseases in dogs, and suggest where to look to find the cause of a problem.

The ITCHY SKIN DISEASES
are characterized by constant scratching, biting at the skin and rubbing up against objects to relieve the itch.
The next diseases are characterized by HORMONE-RELATED AND OTHER DISEASES WITH HAIR LOSS with few if any other symptoms. Hair loss can mean impaired growth of new hair, in which case it usually involves specific areas or the entire coat. Or you may see patches of hair loss on various parts of the body. In general, hair loss caused by hormonal diseases is symmetric (the same on both sides of the body), while that caused by parasites and other causes is asymmetric.

AUTOIMMUNE and IMMUNE-MEDIATED SKIN DISEASES, characterized by blebs. Blebs, also called vesicles, are blisters that contain clear fluid. Large ones are called bullae. All tend to progress through rubbing, biting and scratching, eventually producing skin erosions, ulcers and crusts. Look for these changes to appear first on the face, nose, muzzle and ears. During the course of grooming, playing with or handling your dog, you may discover a lump or bump on or beneath the skin.

LUMPS AND BUMP OR BENEATH THE SKIN. NZYMES® powerful formulas have proven their helpfulness in Vet studies, with nutrition conscious veterinarians and pet owners who have used this powerful formula for years to help strengthen the immune system, reduce pain, restore mobility and increase vitality in animals of all ages.

Allergic contact dermatitis: Same as contact dermatitis, but rash may spread beyond area of contact. Requires repeated or continuous exposure to allergen (such as wearing a flea collar).  

Canine atopy: Severe itching that occurs in young dogs and begins in late summer and fall. Caused by seasonal pollens. Occurs in mixed breeds as well as purebreds. Common.

Chiggers: Itching and severe skin irritation between toes, and around the ears and mouth. Look for barely visible red, yellow or orange chiggers.

Contact dermatitis: Red, itchy bumps and inflamed skin at the site of contact with chemical, detergent, paint or other irritant. Affects feet and hairless parts of the body.

Damp hay itch (Pelodera): Red pimple like bumps on skin. Severe itching. Occurs in dogs bedded on damp hay and similar grass.

Flea allergy dermatitis: Red, itchy pimple like bumps over the base of the tail, back of rear legs and inner thighs. Scratching continues after fleas have been killed.

Fleas: Itching and scratching along the back, around the tail and hindquarters. Look for fleas, or black and white gritty specks in hair (flea feces and eggs).

Fly-bite dermatitis: Painful bites at tips of erect ears and bent surfaces of floppy ears. Bites become scabbed, crusty-black and bleed easily.

Grubs: Inch-long fly larvae that form cyst like lumps beneath the skin with a hole in the center for the insect to breathe. Often found beneath chin or along abdomen. Lice: Two-millimetre-long insects, or white grains of "sand" (nits) attached to hair. Not common. Found in dogs with matted coats. May have bare spots where hair has been rubbed off.

Lick granuloma (acral pruritic dermatitis): Red, shiny skin ulcer caused by continuous licking at wrist or ankle. Usually seen occurring in large, short-coated breeds. (See Instructions for Yeast Problems)  

Maggots:  Soft-bodied, legless fly larvae found in damp matted fur. Scabies (Sarcoptic mange): Intense itching. Small red spots that look like insect bites on the skin of the ears, elbows and hocks. Typical crusty ear tips. Ticks: Large insects attached to skin. May swell up to size of pea. Found beneath ear flaps and where hair is thin.

Walking dandruff (Cheyletella mange): Occurs in puppies 2 to 12 weeks of age. Large amounts of dry, scaly, flaky skin over the neck and back. Itching is variable.

HORMONE RELATED DISEASES WITH HAIR LOSS - Back to Top

Cortisone excess: Symmetric hair loss over trunk and body. Abdomen is pot-bellied and pendulous. Seen with Cushing's syndrome. In some cases the dog is taking steroids.

Growth hormone-responsive alopecia: Bilaterally symmetric hair loss. Begins around puberty. Breed specific involvement.

Hyperestrogenism (Estrogen excess): Occurs in females and males. Bilateral symmetric hair loss in perineum and around genitals. Enlarged vulva and clitoris; in males, pendulous prepuce.

Hypoestrogenism (Estrogen deficiency): Occurs in older spayed females. Scanty hair growth and thinning coat, initially around vulva and later over body. Skin is smooth and soft, like a baby's.

Hypothyroidism: Most common cause of bilaterally symmetric hair loss without itching. Coat is thin, scanty and falls out easily. Involves the neck beneath the chin to the brisket, sides of body, backs of thighs and top of tail.

OTHER DISEASES WITH HAIR LOSS -

Acanthosis nigrans: Mainly in Dachshunds. Hair loss begins in armpit folds. Black, thick, greasy, rancid-smelling skin.  

Color mutant alopecia (Blue Doberman syndrome): Loss of hair over the body, giving a moth-eaten look. Papules and pustules appear in areas of hair loss. Also affects other breeds.

Demodectic mange: Localized - Occurs in puppies. Hair loss around eyelids, lips and corners of mouth, giving a moth-eaten look. Fewer than five patches, up to one inch in diameter. Generalized-Numerous patches that enlarge and coalesce. Severe skin problem complicated by pyoderma. Primarily affects young adults.

Nasal solar dermatitis (Collie nose): Loss of hair at junction of nose and muzzle.

Can lead to severe ulceration. Affects dogs with lightly pigmented noses.

Pressure sores (Calluses): Gray, hairless, thickened pads of wrinkled skin, usually over elbows but may involve other pressure points. Caused by lying on hard surfaces.

Ringworm: A fungal infection. Scaly, crusty circular patches 1/2 to 2 inches across. Patches show central hair loss with a red ring at the periphery. Some cases show widespread involvement.

Sebaceous adenitis: Mainly in Standard Poodles. Symmetrical loss of hair over face, head, neck and back. Dandruff-like scales and hair follicle infection can develop. Seborrhea: Dry type - similar to heavy dandruff. Greasy type - yellow brown greasy scales that adhere to hair shafts; rancid odor. (See Instructions for Yeast Problems)  

Zinc-responsive dermatosis: Crusty, scaly skin with hair loss over the face, nose, elbows and hocks. Cracked feet. Caused by zinc deficiency. Arctic breeds most susceptible.


AUTOIMMUNE AND IMMUNE MEDIATED SKIN DISEASES -

Bullous pemphigoid: Similar to pemphigus vulgaris (see below), but usually begins at the junction of skin and mucous membranes. Mouth is commonly involved.

Discoid lupus erythematosus: Affects the flat surface of the nose. Ulceration and depigmentation are characteristic.

Erythema multiforme: Acute eruption of skin and mucous membranes. Often caused by drugs. Characteristic target-like eruptions with red rims and blanching at center.

Pemphigus erythematosus: Similar to pemphigus foliaceus, but restricted to face, head and footpads.

Pemphigus foliaceus: Red skin patches (raacules) that progress rapidly to pustules and then to dry yellow crusts. Usually limited to face (nose, muzzle, around eyes, ears). Crusts adhere to underlying skin and hair. Often becomes generalized. Depigmentation seen in late stages. The feet can become thickened and cracked. Occasionally only the footpads are involved.

Pemphigus vegetans: Flat-topped pustules involving skin folds. Heals with wart-like growths. Pemphigus vulgaris: Vesicles and bullae (small and large blisters) that ulcerate and form thick crusts. Usually found around the lips and in the mouth, but may be generalized. Ulceration of footpads and shedding of nails are common.

Nodular panniculitis: Multiple lumps (like marbles beneath the skin) over the back and along the sides. Lumps open and drain, then heal by scarring.

Systemic lupus erythematosus: Skin involvement similar to pemphigus foliaceus.

First sign may be wandering lameness. Ulceration of footpads is common.

Toxic epidermal necrolysis: Severe, painful skin disease. Blebs and ulcers involve the skin, mucous membranes and footpads. Large sections of skin are shed like a bum.

RINGWORM IN DOGS

Ringworm is a skin disease caused by a fungus (plural: fungi).  Because the lesions are often circular, it was once thought to be caused by a worm curling up in the tissue.  However, there is no truth to that; it has nothing to do with a worm.

There are four fungal species affecting dogs which can cause the disease that we call ringworm.  These may also affect humans.  The fungi live in hair follicles and cause the hair shafts to break off at the skin line.  This usually results in round patches of hair loss.  As the fungus multiplies, the lesions may become irregularly shaped and spread over the dog's body.

The incubation period is 10-12 days.  This means that following exposure to the fungus, about 10-12 days will pass before any lesions occur.  

A.  Diagnosis is made in one of three ways:

B.  Identification of the typical "ringworm" lesions on the skin

C.  Fluorescence of infected hairs under a special light (however, only two or the four species of fungi fluoresce)

D.  Culture of the hair for the fungus.  The last method is the most accurate, but it may take up to 2-3 weeks for the culture to become positive.

Transmission occurs by direct contact between infected and non-infected individuals.  It may be passed from dogs to cats and visa versa.  It may also be passed from dogs or cats to people and visa versa.  If your child has ringworm, he or she may have acquired it from your pet or from another child at school.  Adult humans usually are resistant to infection unless there is a break in the skin (a scratch, etc.), but children are quite susceptible.  If you or your family members have suspicious skin lesions, check with your family physician.

Transmission may also occur from the infected environment.  The fungal spores may live in bedding or carpet for several months.  They may be killed with a dilution of chlorine bleach and water (1 pint of chlorine bleach in a gallon of water) (500 ml in 4 litres) where it is feasible to use it.

There are several means of treatment.  The specific method(s) chosen for your dog will depend on the severity of the infection, how many pets are involved, if there are children in the household, and how difficult it will be to disinfect your pets' environment.  The one's that are appropriate for your situation are marked.

1.  Griseofulvin.  This is a tablet that is concentrated deep in the hair follicles where it can reach the site of active fungal growth.  Griseofulvin should be given daily.  Dogs with active lesions should receive the tablets for a minimum of 30 days.  At that time, your dog should be rechecked to be sure the infection is adequately treated.  

These tablets are not absorbed from the stomach unless there is fat in the stomach at the time they are given. This can be accomplished by feeding a high fat diet, such as a rich canned dog food or a small amount of fat trimmings from meats (often available at the meat departments of local grocery stores upon request of the butcher) or by allowing the dog to drink some rich cream. This is the most important part of the treatment.  If you are not successful in giving the tablets, please call us for help.  

If you are aware of fat consumption having caused a problem for your dog in the past or if your dog has had an episode of pancreatitis, bring this to our attention immediately.

2.  Topical antifungal medication.  Apply one of these products to the affected areas once daily for 10 days.  Do not risk getting it in your dog's eyes by treating lesions very near the eye.

3.  Baths using an antifungal shampoo.  A bath should be given 3 times on an every other day schedule. Bathe exposed but unaffected pets once.  These baths are important in getting the spores off the hairs so they do not drop into the environment and result in re-exposure.  A lather should be formed and left on for five minutes before rinsing.  

4.  Lime Sulfur Dip.  This should be done twice weekly for the first two weeks then once weekly for 4-6 weeks.  Lime sulfur dip should also be applied to other pets (dogs or cats) in the household to prevent them from being affected.  If they develop ringworm lesions, they should begin on griseofulvin.  You should gloves when applying the dip.  This is an effective form of treatment, but the dip has an objectionable odor and can tarnish jewellery.

5.  Shaving of the dog's hair.  This will remove the infected hair.  We recommend this only when the infection is extensive.

Treatment will not produce immediate results.  The areas of hair loss will get larger before they begin to get smaller.  Within 1-2 weeks, the hair loss should stop, there should be no new areas of hair loss, and the crusty appearance of the skin should subside and the skin look more normal.  If any of these do not occur within two weeks, your dog should be checked again.

Infected pets remain contagious for about three weeks if aggressive treatment is used.  Contagion will last longer if only minimal measures are taken of if you are not faithful with the prescribed approach.  Minimizing exposure to other dogs or cats and to your family members is recommended during this period.

When treatment is completed, ringworm should be cured.  Although a carrier state can exist, this usually occurs because treatment is not long enough or aggressive enough or because there is some underlying disease compromising the immune system.

I have given you a comprehensive list of skin ailments with causes and some treatments for your "canine library!"  Some of the information can be applied to your dog's current symptoms and some you may need to refer to in the future.  

My best suggestion is to work with your vet, as hair loss in several places can indicate a more serious problem.  The first thing I would do is check for thyroid disease and food allergies.  You vet will hopefully have some idea about what is causing the problem and if he doesn't then he should refer you to a specialist.

Back to Top

Home