Why does my dog have a skin rash?

Causes of Skin Rashes in Dogs

The skin is the largest organ of the body. Its primary function is to protect the body from the external environment by acting as a barrier between the internal organs and the outside world. The skin can reveal a lot about a dog’s health and well-being. It’s very sensitive to changes in the dog’s environment as well as in the body. Rashes are just one of the symptoms of skin sensitivity.

The list of factors that can cause skin rashes in dogs is quite long. Among the most common are:

• Skin infections - can be caused by bacteria, viruses, or fungi (yeast)
• Inflammatory conditions
• External parasites such as fleas, mites, etc.
• Allergies
• Genetic abnormalities
• Endocrine problems such as hypothyroidism and Cushing’s disease
• Environmental causes such as Eucalyptus, Poison Ivy, Stinging Nettles, etc.
• Soap, household cleaning products, etc.
• Intestinal worms
• Sunlight or heat
• Exercise-induced urticaria
• Stress
• Vaccination
• Medication

Rashes Caused by Infections

Skin rashes in dogs can be caused by bacterial or fungal (yeast) infections. Bacterial infections are often accompanied by pimple-like lesions that may contain pus. The medical term for this is “pyoderma” (Greek: “pyo” is pus and “derma” is skin). The rashes may also be accompanied by dandruff - skin that is dry, crusty, and flaky. Hair loss and itching may also be a problem. Puppies are especially prone to pyoderma in areas of their bodies that have less hair, such as their groin and armpits.

Fungal infections, such as yeast dermatitis (Malassezia dermatitis), can cause skin rashes, changes in skin pigmentation, chronic ear infections, scaling, and flaky skin. The dog also has a distinct musty smell.

Ringworm is another type of fungal infection that is characterized by red, circular rashes. Ringworm lesions are not usually itchy, but skin inflammation may be present. Also, ringworm is very contagious. It can easily be transmitted to humans and other pets.

Skin Allergies

Rashes on a dog’s belly can be a symptom of an allergic reaction to allergens that are present in the environment, flea bites, or food allergies. These rashes can be itchy and when your dog scratches them, it can cause breaks in the skin which could become avenues for secondary bacterial infections, making the problem more complicated.

Some dogs are more prone to develop allergic reactions to food and airborne allergens. These include Golden Retriever, English Bulldog, Maltese, Bull Terrier, German Shepherd, and Lhasa Apso to name a few.

The symptoms of plant allergies in dogs can range from very mild skin rashes to more serious issues involving major internal organs of the body. A dog may be allergic to the plant’s pollen, sap, oil, or other plant components.

Skin Parasites

Skin rashes are common during a flea, tick, or mite infestation. A dog that is allergic to flea saliva can suffer from intense itching even just after a flea bite or two. When these rashes become irritated as a result of persistent scratching, licking, and chewing, they can expose your pet to secondary bacterial and/or yeast infections.

Intestinal Worms

Skin irritation and itching can also be present in dogs with a severe infestation of intestinal parasites. Parasitic diseases are often considered a classic cause of urticaria. Current data indicates that skin allergies in dogs may be associated with certain stages of the parasites' lifecycle.

Genetic Causes of Skin Rashes in Dogs

Some dog breeds are more prone to developing skin rashes compared to other breeds. These include Labrador and Golden Retrievers, Bulldogs, Cocker Spaniels, German Shepherds, and Doberman Pinschers to name a few.

For instance, primary seborrhea or dandruff is a hereditary disorder in Cocker Spaniels. Golden Retrievers are prone to congenital ichthyosis, and Samoyeds can get zinc-responsive dermatosis.

Endocrine (Hormonal) Disorders

Hormonal imbalances and conditions involving the endocrine system can be serious underlying causes of skin rashes in dogs. The most common endocrine disorders in which skin rashes are one of the symptoms are hypothyroidism and Cushing’s disease (hyperadrenocorticism). Aside from the rashes, other early symptoms also include hair loss and changes to the quality of the dog’s skin. Skin rashes in dogs may appear as pimple-like lesions (pyoderma) or dry scaly skin that may be accompanied by itching, redness, weeping, scabbing, and inflammation.

Heat Rash

When the environmental temperatures start to rise, the heat can cause some dogs to develop a rash. This is especially true in dogs that are overweight or obese and those with a lot of skin folds and wrinkles, like the Shar-Pei. Rashes usually develop in the skin folds and on the dog’s belly. Heat rash can increase a dog’s risk of hot spots or acute moist dermatitis which is caused by secondary bacterial infection.

Contact Dermatitis

Rashes develop after the dog has been in contact with something, such as after using a shampoo that contains ingredients that the dog is hypersensitive to. Or the culprit could be the dog’s blanket or even the carpet.

Severe Allergic Reaction (Anaphylaxis)

Anaphylaxis is an immediate, severe, and potentially life-threatening immune response. It can develop within seconds or minutes of exposure to something that your pet dog is allergic to, such as bee or wasp stings and even vaccination. Prompt veterinary attention is required.

Stress

Stress has been linked to many skin problems in dogs. This can lead their fur to fall out, for them to excessively lick or bite themselves, or even cause rashes if their anxiety is really heightened.

Medication Side Effects

Some dogs exhibit a hypersensitive reaction to certain medications. A common example is antibiotics. The highest incidence of allergic reactions to antibiotics has been associated with penicillins and sulfonamides. Hives and raised welts may also develop as a result of drug-related skin reactions. Aside from antibiotics, drugs that are known to cause skin reactions in dogs include NSAIDs, anti-cancer medication, topical medications, and parasite preventatives.

Read more:

How to Tell if Your Dog has Seasonal Allergies

Allergy Tests for Dogs

Why is my dog itchy?

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