In dogs, allergies work much like they do in humans. When a dog is exposed to allergens, including pollen, dust mites, mold, certain foods, and more, their immune system mistakenly identifies the allergen as harmful and releases histamines in response. Histamines make blood vessels expand, leading to swelling of skin structures and itching. 

Bacterial and fungal infections are common in dogs and can affect their skin, ears, and other parts of the body. Your veterinarian may be able to diagnose an infection easier than allergies, as many infections lead to lesions and redness in addition to hair loss. 

Besides overgrowth of normal skin bacteria, bacterial and fungal infections an be picked up from a canine's environment and require a veterinarian's exam and diagnostic testing for to achieve a diagnosis and determine appropriate treatment.

These pesky culprits are all too happy to latch onto a dog’s coat. They are plentiful in outdoor environments, especially grassy and wooded areas. Since most dogs get several walks outside each day, they're likely to encounter blood-feeding insects along the way. And as fleas, ticks, and other biting insects can spread diseases, it's important to take preventative measures by using veterinary-prescribed topical or oral flea, tick, and heartworm preventatives.

Symptoms vary depending on the cause of the hair loss and scratching, whether it be allergies, infections, or parasites. 

• Chewing, licking, and scratching, often affecting the paws, ears, and belly.
• Red or inflamed skin, indicative or inflammation, particularly in areas where the dog licks or scratches.
• Hair loss or thinning, particularly around the paws, undersides of the chest and abdomen, armpits, and groin.

• Chewing, licking, and scratching, sometimes accompanied by gastrointestinal symptoms like vomiting or diarrhea.
• Inflamed skin, often around the face and anus where food allegens enter or leave the body. But, as the mouth and tongue can spread food allergens around the body any accessible body part could be affected.
• Hair loss or thinning in specific areas, often related to chronic scratching or biting.

• Red, inflamed skin with pustules (“whiteheads”) or brown or tan crusts (dried-out pustules).
• Chewing, licking, and scratching, often leading to hair loss.
• Foul odor from affected areas.

• Circular patches of hair loss with a red, inflamed border.
• Itching or mild discomfort.
• Flaky or scaly skin in affected areas.

• Intense itching around the tail, neck, and along the back with or without the presence of fleas on the skin surface.
• Red, inflamed skin.
• Hair loss in patches, especially where the dog scratches or bites.
• Flea dirt (black specks of dried blood that dissolve and turn light orange-red when dabbed with a moist, light-colored cloth) in the fur and on the skin surface.
• Secondary skin infections or hot spots (areas of inflammation and hair loss) from excessive scratching.

• Visible ticks on the skin, often in areas like the the face, ears, between the toes, or any place that comes into contact with brush on which ticks wait to attach to a dog.
• Red, inflamed skin around the bite site.
• Itching, chewing, and licking, especially if the tick is in a sensitive area.

• Patchy hair loss, usually around the eyes, mouth, and legs. 
• Intense itching 
• Hair loss in patches, especially around the ears, elbows, and abdomen.

“My dog is itching and losing hair?” It’s a question I hear often in my practice, and always leads me to a few questions: How long has this been happening? Have they been in any new environments? Have there been any recent food or treat changes? Do you notice any particular patterns associated with the itching? 

As a pet parent, the best thing you can do when you start to see symptoms is to observe and document them. Here’s a breakdown of a typical course of action you can take if you notice abnormal itching or hair loss in your pet.

When I see a pet for itching and hair loss, I first look for signs of infection, such as redness, swelling, pustules, or the presence of fleas and ticks. I’ll feel the skin for mass-like lesions (bumps, lumps, etc.) or unusual textures. In some cases, I’ll recommend tests such as skin impression smears or scraping for cytology (microscopic evaluation), bacterial and/or fungal culture, blood testing for internal organ function, or allergy testing. 

Or, I may prescribe oral, topical, or injectable medications like antibiotics, anti-fungals, antihistamines, anti-parasitics, steroids, allergy immunotherapy, or itch-reducing treatments. If I suspect food allergies, I may recommend an elimination diet to identify and avoid allergy triggers.

When I need to dig a little deeper to get to the bottom of an issue, I have a few options. One is doing skin scrapings, which I analyze under a microscope. This often tells me what kind of bacterial or fungal infections may be contributing to the clinical signs. I may send swabs of the skin surface or discharge to a laboratory for bacterial and/or fungal culture. In other cases, I may recommend allergy testing, a process that involves injecting small amounts of allergens into the pet’s skin to observe reactions.

Just as with humans, blood tests can tell us a lot about the root causes of a condition. They help identify systemic issues, infections, and allergic reactions. The most common common tests are Complete Blood Count (CBC) which assesses red blood cells (oxygen transporting cells), white blood cells (managers of inflammation and infection), and platelets (blood clotting cells) and chemistry testing for internal organ function to detect metabolic (endocrine/glandular) disorders that may contribute to skin issues. 

Cushing's Disease (Hyperadrenocorticism) and Hypothyroidism are the two most-common metabolic disorders that can correlate with abnormal skin and coat health. Serum allergy testing (a blood test that can determine a dog's sensitivity to certain allergens) can also shed some light on skin problems, but skin allergy testing is more precise.

A chemistry panel helps assess organ function and detect metabolic disorders that may contribute to skin issues. Other tests for a dog losing hair from itching can be thyroid function tests, heartworm tests, and serum allergy testing (a blood test that can determine a dog’s sensitivity to allergens).

After consulting with a vet and determining a treatment plan, you can often take the problem into your own hands. Fleas, ticks, mites, and parasites respond well to topical medications, as well as shampoos and sprays with anti-pest ingredients like pyrethrin. For allergies, antihistamines or corticosteroids can be tried under veterinarian guidance. Skin infections can be treated with topical or oral antibiotics or anti-fungals, or medicated shampoos formulated to treat infection.

The remedies you need are often just a shopping aisle or online cart away. 

Start with a maintenance routine that will help keep your dog’s hair clean and lush. A pet wipe can help your pup keep infection-causing grime away. Also a must: a dog de-shedding brush to remove loose fur and debris and promote a healthy coat. 

To soothe irritated skin, use an anti-itch pet shampoo that contains active medicated ingredients to help alleviate itching while gently cleansing to remove excess oil and skin crusts/flakes. And for bacterial and fungal infections (including ringworm), a veterinarian-formulated shampoo can treat while promoting healthy skin.

Luckily, there are plenty of ways to help your dog prevent uncomfortable itching and scratching at home. 

• Regular grooming is key to reducing excessive chewing, licking, and scratching, as is giving your dog regular baths and routinely brushing their coat. 
• If your pet spends time outside, rely on veterinary-prescribed oral and topical flea and tick treatments or collar to protect their skin and coat. 
• Address allergies by identifying triggers and avoiding them, whether they are environment- or food-related. 
• Keep your home clean and free of dust, mold, and other potential by regularly vacuuming, washing capets, pets beds, and upholstery, and changing air filtration systems.
• Of course, regular checkups at the veterinarian will keep you on top of things!

Now that you know a little more about this common issue of itching and hair loss in dogs, the next time you see them scratching themselves, you don’t need to scratch your head. Instead of saying, “My dog is itching and losing hair but no fleas can be found––what gives?” you have the guidance you need to make sure your four-legged family member is healthy and comfortable.