Crusty Scabs on Dogs: Top Causes and What To Do [Vet Advice]

I saw my share of skin problems when I was in practice, and crusty scabs on dogs were among them. Whenever an owner brought their pooch in for crusty black or yellow scabs, I would explain that there are various causes for the lesions. After examining my patient and evaluating the scabs, I recommended a course of treatment.

In this article, I’ll explain the different reasons for scabs on dogs and what you can do to help your dog. To help you know when it’s time for treatment, I’ll describe the signs that tell you it’s time to head to the vet and what your doctor can do for your dog. 

What’s a “crusty” scab?

Scabs are protective coverings over damaged skin. When your dog’s integument suffers an injury, platelets in the blood travel to the area and join with fibrin proteins and red blood cells to form a clot. The clot seals off broken blood vessels and prevents further blood loss once the damaged tissue is sealed off, the clot contracts and hardens to form a crust. 

What does it mean if the scab is yellow or black?

Crusty scabs come in a variety of shapes, sizes and colors:

• Black crusty scabs: when clots dry and harden, they often appear black. Read top reasons for black scabs on dogs.
• Yellow crusty scabs: scabs on dogs can also have a yellow hue if your dog has seborrhea. Bacterial and yeast skin infections can cause crusty yellow scabs on dogs. 

Depending on the underlying cause, scabs may manifest as bumps, blisters, or patches of dry, flaky skin.

Types of scabs that are crusty and/or raised 

Crusty scabs on dogs often appear over a generalized area and can vary in appearance, but they usually manifest as blisters, bumps, or dry, flaky scabs. There are several causes of crusty raised scabs in dogs.

1. Injury

When dogs sustain a wound or cut, the body forms a protective scab to allow the injury to heal. Usually, these lesions will appear as a dark brown to black covering because they consist of dried blood and other materials. Black crusty scabs on dogs may be painful in the early stages and become itchy as they heal. Eventually, your pooch may try to nibble at the scab or rub it against a wall or furniture. Learn more about: 4 Dog Wound Healing Stages [With Pictures].

2. Self Trauma

Self-trauma is an injury where your dog excessively licks or scratches his skin. The lesions from self-trauma are common under the armpits and along the flanks. Causes of extreme itching that result in crusty scabs on dogs include:

• Allergies
• Skin parasites
• Infections

Below is an example of an incision that has not healed well because of the dog’s excessive licking of the area.

3. Skin Parasites

Skin parasites that can trigger itching and crusty yellow or black scabs on your dog include fleas, mites, and ticks. 

• Fleas – Some dogs react to flea bites and have dry, itchy skin. When this happens, your pup will chew or bite along the back and base of the tail which leads to hair loss. Read our article: how to tell if your dog has fleas.
• Mites – Mites can cause two types of mange in dogs, demodectic and sarcoptic. Demodectic mange usually manifests with red, scaly skin, hair loss, and infections that create yellow crusty scabs on your dog. Read our article: what dog mites (mange) look like in dogs. With sarcoptic mange, dogs have:
  • Extreme itching and rashes
  • Reddened skin
  • Hair loss
  • Crusty yellow scabs
  • Thickened skin
• Ticks – When ticks bury their heads under your dog’s skin, it causes itching. Black crusty scabs on your dog form when he continuously scratches at the area.

4. Allergies

Whether your dog reacts to food, chemicals, or environmental allergens, he’s going to scratch at the affected area. The continual itching leads to open sores and black, crusty scabs on your dog. Learn more: Common types of skin allergies. In addition to constant itching, other signs of allergies can include:

•  Hives
• Swelling around the face, ears, and earflaps
• Reddened skin
• Chronic ear infections
• Sneezing
• Diarrhea/vomiting

5. Infection

Bacterial and yeast skin infections can cause crusty yellow scabs on dogs. 

• Bacteria – When bacteria such as Staphylococcus infect your dog’s skin, you may observe
  • Crusty, yellow scabs
  • Itching
  • Pussy discharge
  • Dry, flaky skin patches
  • Patchy hair loss
  • Redness and inflammation
  • Deep infections may have swelling 

• Fungus/Yeast – When yeast or fungus infects your dog’s skin, it causes:
  • Crusty black or yellow scabs
  • Itchiness
  • Smelly skin
  • Greasy coat
  • Yellow-green discharge
  • Thickened skin

6. Seborrheic dermatitis

In seborrheic dermatitis, the canine sebaceous gland produces too much sebum, and this causes:

• Crusty, thickened areas on the skin
• Red, itchy skin
• Dry, flaky skin patches
• Hair loss
• Yeasty odor

Can I just monitor my dog and wait?

Many times, an isolated scab is the result of an injury and should heal on its own. As long as your dog isn’t showing signs of pain and inflammation, or other concerning symptoms listed below, you should be able to monitor your dog at home. Regular crusty scabs on dogs due to injury generally heal in about 3-14 days.

Signs that your dog’s scabs need veterinary attention

Many scabs from injuries can heal without medical attention, but there are times when you should seek veterinary help for your dog’s scabs. You should bring your pup to the clinic for an exam and treatment if you notice the following:

• Continual licking/itching – When your pup is licking, scratching, or rubbing the area excessively, or itching lasts for more than a few days, he can make it worse or trigger an infection.
• Discharge/signs of infection – If the scab is oozing pus or a yellow-green discharge, it’s likely there’s an infection that requires attention. Read our article about incision infections in dogs.
• Inflammation/redness – When the scab has red edges or other signs of inflammation including pain and feeling warm to the touch, it should be examined by a vet.
• Scabs keep coming back – If any home remedies you use for scabs don’t help, and the scabs recur, there may be an underlying condition causing the scabs. 
• Widespread or multiple scabs – When dogs have widespread scabs, it’s usually not related to an injury. Your veterinarian can help you figure out the underlying condition that’s causing the crusty scabs on your dog.
• Extensive injuries – When a single wound is large, it may require stitches to promote healing.  

Some things you can do at home to help with crusty black or yellow scabs

 When your dog’s scabs appear to be isolated and related to an injury, there are some things you can do to help them heal. 

• E-collar – If your pooch is licking or biting the scab, you can use an Elizabethan collar to prevent self-trauma to the area. Continual irritation of the skin from licking, scratching, or biting causes a release of histamines which trigger further inflammation. By keeping your dog from the affected area, you may be able to reduce itchiness. 

• Keep it clean – You can gently flush or bathe the scab with a saltwater solution to remove loose skin, dirt, and hair. Do not scrub the scab or attempt to remove the protective covering. 

• Diet/supplements – Dietary deficiencies can cause skin conditions and scabs. Ensure your pup is on a balanced diet that provides all the essential nutrients. You can also supplement with fish oil to support healthy skin. For allergies, you may also consider feeding a hypoallergenic diet.

• Antifungal/medicated shampoos – If you suspect a bacterial or yeast infection is causing crusty black or yellow scabs on your dog, try using a medicated shampoo. Check with your veterinarian for the best option for your dog’s condition.

• Anthelmintics – If your pup suffers from skin parasites, treat him with an appropriate anti-parasitic medication to eliminate the pests. 

• OTC medications – You may be able to use Benadryl or a topical antibacterial/antifungal ointment to help clear up the underlying causes of your dog’s scabs. 1-2 mg/pound of regular Benadryl can reduce allergic symptoms and itching. Do not give Benadryl-D to your dog. Check with your veterinarian for recommendations about topical medications.

Most scabs from wounds or injuries usually resolve in 3 days to 2 weeks depending on the severity of the initial lesion. If you’re treating yellow or black crusty scabs on your dog at home, you should see improvement in your pup’s condition in the first few days. If your dog’s scabs are not starting to heal after about 3-5 days, you should contact your veterinarian.

How long does it take for crusty scabs to heal?

If your pooch has a simple scab without an underlying condition, it should normally heal within a few weeks. When your pooch suffers a wound, blood collects at the injury site to form a clot. As the clot dries up, it forms a dark, crusty scab that protects the injured skin. Depending on the severity of the wound, the scab will dry and become harder in a matter of days to a few weeks. The hard, crusty covering gives the skin time to repair itself. As healthy skin grows, the scab detaches and falls off.

When underlying conditions like allergies, parasites, or infections exist, the healing process is affected. So, if your dog’s scabs never seem to heal, or if they take several weeks to months to improve, you should talk to your vet. There’s probably more going on underneath the surface.

How can my vet help with crusty scabs on my dog?

When you bring your dog to the veterinarian because he has crusty scabs, the doctor will begin by taking a history of your pup’s condition. It helps if you know what type of questions he will ask because it saves time. You can come prepared with answers. Expect him to ask questions like:

• When did you first notice the scabs on your dog?
• Have you noticed any changes in the scabs/have they gotten worse?
• Have you seen scabs anywhere else on your dog?
• Do you know what causes the scabs/was there trauma?
• Does your dog have any allergies?
• Have you noticed any other symptoms or changes in your dog’s behavior?
• Is your dog licking or itching at the scabs?
• Have you tried any treatments or remedies at home? What are they?

After collecting a thorough history of your dog’s scabs, your veterinarian will conduct a physical examination. Depending on the doctor’s findings, he may run diagnostic tests including:

• Allergy testing
• Bacterial cultures
• Blood work
• Fungal culture
• Skin scraping
• Skin biopsy

Treatment will depend on the diagnosis.

• If allergies are suspected, your veterinarian may prescribe antihistamines and anti[inflammatory medications. Additionally, he could recommend feeding a hypoallergenic diet.
• For bacterial infections, your vet will prescribe topical and/or oral antibiotics. He may also recommend a medicated shampoo to help reduce itching and inflammation.
• Similarly, for fungal or yeast infections, the doctor will prescribe topical antifungal ointments and possibly a medicated shampoo.
• When parasites are involved, the doctor will use anti-parasitic drugs to kill the pests and may also prescribe antiinflammatories to help calm irritated, itchy skin.
• For dogs suffering from seborrhea, the vet will prescribe medicated shampoo and corticosteroids. If there are secondary infections, he will also treat your dog with antibiotic or antifungal medications.

Frequently asked questions

What are the most likely causes if my dog has crusty scabs on his back?

The most likely causes of crusty scabs on a dog’s back are 

• Skin parasites
• Allergies
• Bacterial infections
• Yeast infections.

What are the most likely causes of crusty scabs around my dog’s mouth?

The most likely causes of crusty scabs around your dog’s mouth are:

• Canine acne
• Allergies to food or household cleaning products
• Skin parasites(mites)
• Bacterial or fungal infections
• Dehydration