7 Reasons for Rapid Hair Loss in Pets

Hair loss is one of the most common reasons pet parents take their dogs and cats to the veterinarian. Often pets that have rapid hair loss also have other, more worrisome problems like scratching and licking. You may also notice a new odor emanating from your furry friend. There are many causes for these skin problems that cause hair loss.

The good news is that some of the most common causes of your sudden hair loss can be easily dealt with. Most pets regrow their lush, healthy coats quickly after the underlying problem is resolved. Here are a few of the most common causes and what you need to know about them:

1. Fleas

Many people are shocked when the culprits are fleas for their pet’s hair loss. These frustrating little critters can definitely cause hair loss. They are typically focused around the tail and abdomen but can occur anywhere. Depending on how sensitive (or allergic) your pet is to fleas, significant itching and hair loss can occur if just 1-2 fleas are present. In addition to these things, you may also notice the following symptoms:

  • Redness of the skin.
  • Rind black dirt-like material in your pet’s fur (flea excrement)

Fleas greatly prefer warm, humid environments, so more tropical areas are prone to year-round flea issues. Adult fleas only represent about 5% of the entire flea population in your home environment. Female fleas can lay up to 50 eggs per day for the 3 or so months of her life. With that many eggs, the flea population can get a little out of control quickly. The good news here is that fleas are a readily treatable condition. There are many quality flea control products on the market. That, along with routinely cleaning your home, can help keep that flea population under control and eliminate related skin issues for your pet.


2. Mites

Several different species of mites exist. Each one may create varied issues, but one common symptom of most mite infections is hair loss.

This may start as small, patches near the head, neck or feet. Over time these can spread over the entire body, leading to open sores or other skin issues. Some mites are contagious and can be passed from pet to pet or even from pet to person. However, some mites are not contagious and are thought to create infection because of a dog or cat’s own genetics.

Most veterinarians can perform a simple test called a skin scrape. During this test, they try to collect mites from the skin surface or hair follicles and examine them under the microscope.

It is worth mentioning, that even when done correctly, this test may still, on occasion, miss mites and need to be repeated. Once a diagnosis is made there are several treatment options available. Your veterinarian may recommend a combination of therapies depending on the extent of disease and presence of other skin issues.

3. Bacterial or Yeast Infections

When we refer to these types of infections, we are commonly referring to the normal bacteria and yeast that are always present on a dog or cat’s skin. These can create an infectious state when the skin is compromised.

This initial issue may occur from something as simple as going for a swim or something more significant like contact irritation or allergies. When the skin’s normal immune response breaks down the bacteria and yeast take advantage of the situation. They may cause everything from hair loss to crusting, thickening of the skin, dark pigmentation and even foul odor.

Once again, this condition usually starts in a small area, then spreads. However, it can pop up very quickly and cover the whole body from the start. The good news is that these conditions are readily treatable.

Sometimes topical therapy, like medicated shampoo, alone is enough to get your pet back to normal. Most veterinary hospitals can perform a test in the hospital to check for the presence of abnormally high numbers of bacteria or yeast on your pet’s skin. More advanced testing such as a culture may be recommended based on your veterinarian’s initial findings.

4. Ringworm

Unlike its name would lead you to believe, ringworm is not a worm, but in fact a type of fungal infection. When most people think of ringworm disease, they often think of the classic red, raised circular lesion like what we see on ourselves. However, in our four-legged family members, the presentation of ringworm can vary widely. Some pets exhibit circular crusty lesions with hair loss while others may have just generalized hair loss or thinning.

A handful of other patients may get severe ulceration or even raised, red, plaque-like structures on their skin. It is even thought that some pets (particularly cats) may carry the ringworm spores on their coat and skin without having any signs of disease at all.

Just like with certain types of mites, ringworm can be spread from pet to pet or from pet to person. Again, depending on the extent of disease and type of infection diagnosed your veterinarian may recommend a combination of topical and oral treatments. To solve the problem, cleaning your home will help eliminate ringworm.

5. Allergies

This is one of the most common causes of chronic or recurrent skin issues. Allergies are a major cause hair loss or hair thinning from licking and scratching.

There are four main categories of allergies:

  • Atopy (environmental allergies)
  • Flea allergies
  • Food allergies
  • Contact allergies

Of these, atopy or allergies to things like pollen or grass are the most common type. While dogs and cats can inhale the pollen or other allergens and get watery eyes, sneezing and a runny nose, they are also very prone to absorbing these allergens through their skin and paws causing redness, itching and hair loss.

Pet owners may notice that this itching and hair loss starts as a seasonal occurrence, then over time becomes a persistent issue. Most veterinarians will make a presumptive diagnosis of atopy based on the symptoms and exam findings. However, in order to obtain a true diagnosis, other allergens must be eliminated as a potential cause.

A scratch test (intradermal skin test) is often used to measure each dog or cat’s response to different allergens. Despite some of the recent hype about food allergies in dogs and cats, they are actually a relatively rare finding.

Less than 5% of allergic pets have food allergies. To diagnose this type of allergy, your veterinarian may recommend that you feed him a specific diet for a set amount of time. It is critical to work closely with your veterinarian when attempting to diagnose food allergies as there are only a handful of special diets restricted enough for a true food trial.

Many other treats or table scraps could affect the results of a food trial if fed. Depending on the type of allergy your pet has, there are many potential treatments available. Your veterinarian can work with you to determine the most effective regimen to keep allergies at bay in your pet.

6. Endocrine (hormone problems)

This cause of hair loss refers to a handful of conditions caused by internal changes to chemical or hormonal balances. For example, in dogs, the two main endocrine conditions causing hair loss are hypothyroidism and Cushing’s disease.

Hypothyroidism occurs when the thyroid gland fails to produce enough thyroid hormone. Common findings with low thyroid level are a tendency towards weight gain, decreased activity level, a possible decrease in appetite and hair thinning. One distinctive trait of hypothyroidism is the loss of hair specifically on the tail. This is sometimes referred to as a “rat tail” because of the striking resemblance to a hairless rodent tail.

Cushing’s disease occurs when there is an overproduction of a stress hormone called cortisol. This can cause a wide range of symptoms including hair loss, weight gain, panting, increased thirst and urination. In this case, the hair coat just appears thinner and the hair is often more brittle and dry than normal.

In cats, hyperthyroidism (production of too much thyroid hormone) and diabetes are 2 of the most common endocrine conditions to cause pets to lose hair. With these diseases, the hair coat is usually unkempt, and their fur comes out more easily and is more brittle than usual. With all endocrine disorders, the changes are generally spread over most of the body (except for the rat tail in hypothyroidism) and are not usually patchy.

7. Behavioral

Much like with people, our pets can develop unhealthy habits when stressed, anxious or bored. One potential habit, especially with our cat friends, is that they may over-groom. This obsessive licking or chewing can cause trauma to their fur.

Often, the coat looks shorter or thinner, and the skin becomes more visible, rather than truly missing hair. Sometimes we will observe our four-legged family members doing this licking. Other times, this behavior will only be done in private. Unfortunately, anxiety may manifest in different ways and is very difficult to diagnose as the true cause of hair loss.

Some pets may show other signs of stress such as panting, pacing or destructive tendencies with dogs and hiding, scratching or inappropriate litter box habits with cats. However, there are many pets whose only sign of anxiety is the hair loss.

In these pets, it is important to rule out several other causes of hair loss before landing on anxiety as the cause. If these cases are mild, you can attempt to modify the environment or adjust activities in your pets’ lives to alleviate the stress they may be feeling. In more severe cases, anti-anxiety medications can be used in the short or long-term to reduce stress.

Wrap Up

Rapid hair loss can certainly be caused by a wide range of issues. If you are doing everything at home to care for your pet’s coat, it is best to see your veterinarian if your pet is experiencing any hair loss. This includes providing a high-quality diet and using pet-friendly shampoos. Many of the conditions that cause this rapid loss of hair are easily treatable. Early detection and testing can go a long way towards helping your pet recover.

About the Author
Danielle Churchill, DVM is a veterinarian and medical director of West Park Animal Hospital in Westchase, FL. She graduated from University of Florida College of Veterinary Medicine in 2010 and through a variety of veterinary experiences, she has developed a keen knowledge of a wide range of animal health topics. She has a particular interest in dentistry, internal medicine, and progressive quality of life care, and is known amongst her colleagues as a thoughtful, caring veterinarian.


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