Symptoms & Diagnosis

Why Does My Dog Have Bumps on Their Skin? Causes, Types, and When to Worry

By Emiel Maddens · Reviewed in consultation with licensed veterinary professionals · Updated April 2026 · 10 min read

Dog with visible raised bumps on the skin, a common dermatologic complaint in veterinary practice

Key Takeaways

Skin bumps in dogs range from completely benign (insect bites, histiocytomas) to potentially serious (mast cell tumors), so accurate identification matters.
Bacterial folliculitis, an infection of the hair follicles, is the single most common cause of small red bumps on a dog's skin.
Hives (urticaria) produce rapid-onset, widespread raised welts and usually indicate an acute allergic reaction requiring prompt attention.
Any new lump that is firm, grows rapidly, changes shape, or does not resolve within 2 to 3 weeks should be evaluated by a veterinarian with fine-needle aspirate cytology.
Many benign bumps resolve on their own or with simple treatment, but a hands-off approach without a diagnosis can delay detection of something more serious.

Finding a bump, lump, or raised spot on your dog's skin is one of the most common reasons pet owners schedule a veterinary visit, and rightfully so. Skin lumps and bumps are among the most frequent dermatologic findings in dogs, and the list of possible causes is long. The good news is that the majority are benign. The challenge is that some look nearly identical to serious conditions on the surface, which is why visual identification alone is unreliable.

This guide covers the most common types of skin bumps in dogs, explains what each looks like, and clarifies which ones need veterinary attention versus which ones you can monitor at home. The goal is to help you provide your vet with useful information while avoiding both unnecessary panic and inappropriate complacency.

The 8 Most Common Causes of Skin Bumps in Dogs

Skin bumps in dogs fall into several broad categories: infectious, allergic, traumatic, benign growths, and malignant tumors. Here are the most common types, roughly ordered by prevalence:

1. Bacterial Folliculitis

Folliculitis is an infection of the hair follicles, most commonly caused by Staphylococcus pseudintermedius. It produces small, red, raised bumps (papules) that may have a pustule (white or yellow head) at the center. The bumps often progress to circular areas of hair loss with a scaly border, sometimes called epidermal collarettes. Folliculitis is rarely a primary problem. It almost always develops secondary to an underlying condition like allergies, hormonal disease, or a compromised skin barrier. Treating the bumps without addressing the root cause leads to recurrence.

2. Hives (Urticaria)

Hives are raised, flat-topped welts that appear suddenly and can cover large areas of the body within minutes. They are caused by an acute allergic reaction, most commonly to insect stings, medications, vaccines, or new foods. Individual hives are typically 1 to 5 centimeters in diameter, and the fur may stand up over them, making them easier to feel than see. Most episodes resolve within 24 to 48 hours, but severe reactions can progress to facial swelling (angioedema) or anaphylaxis, which requires emergency treatment.

3. Insect Bites and Stings

Flea bites, mosquito bites, ant stings, and spider bites all cause localized swelling and raised bumps. Flea bite dermatitis, in particular, produces clusters of small, itchy papules, typically concentrated on the lower back, tail base, and inner thighs. A single flea can trigger an intense reaction in a flea-allergic dog. The bumps from insect bites are usually itchy, self-limiting, and resolve within a few days once the source is eliminated.

4. Canine Acne

Canine acne (chin folliculitis and furunculosis) presents as red bumps, pimples, and sometimes draining lesions on the chin and lips. It is most common in young dogs of short-coated breeds like Boxers, Bulldogs, Dobermans, and Great Danes. The condition is caused by trauma to hair follicles from friction, combined with secondary bacterial infection. Mild cases may only need topical benzoyl peroxide, while severe cases require oral antibiotics.

5. Histiocytomas

Histiocytomas are benign tumors of immune cells (Langerhans cells) that are most common in dogs under 3 years of age. They appear as small, round, firm, hairless, button-like bumps, usually on the head, ears, or legs. They typically grow rapidly over 1 to 2 weeks, then spontaneously regress and disappear within 2 to 3 months. Because they can look similar to mast cell tumors, cytology is recommended to confirm the diagnosis before adopting a wait-and-see approach.

6. Mast Cell Tumors

Mast cell tumors (MCTs) are the most common malignant skin tumor in dogs. They are notoriously variable in appearance, mimicking everything from a bug bite to a lipoma. They can be soft or firm, small or large, and may fluctuate in size due to histamine release (the Darier sign). Because MCTs can look like virtually anything, the veterinary mantra is: if you cannot identify a skin lump, aspirate it. Fine-needle aspirate cytology can diagnose most MCTs quickly and affordably. Early detection and surgical removal significantly improve outcomes.

7. Lipomas

Lipomas are benign fatty tumors that develop under the skin. They are soft, mobile, non-painful, and covered by normal-appearing skin. They are most common in middle-aged to older dogs and in overweight animals. Lipomas rarely cause problems unless they grow large enough to impede movement or develop in a location that makes surgical removal more complex. A fine-needle aspirate can confirm the diagnosis and distinguish a lipoma from a more concerning mass.

8. Sebaceous Cysts (Epidermal Inclusion Cysts)

Sebaceous cysts are firm, round, well-defined bumps in the skin that contain a thick, cheese-like material. They form when a sebaceous gland or hair follicle becomes blocked. They are benign and usually cause no problems unless they rupture, in which case they can become inflamed and secondarily infected. Ruptured cysts require cleaning and sometimes antibiotics. Surgical removal is curative for recurrent or problematic cysts.

Veterinarian examining bumps on a dog's skin with a dermatoscope

Which Breeds Are Most Affected?

Some breeds are predisposed to specific types of skin bumps due to their genetics, skin structure, or immune tendencies:

Boxer: Among the breeds with the highest rates of mast cell tumors, and also prone to histiocytomas and folliculitis from atopy.
Labrador Retriever: Susceptible to mast cell tumors, lipomas, histiocytomas, and folliculitis secondary to their high allergy prevalence.
Golden Retriever: Elevated rates of mast cell tumors, lipomas, and allergy-driven folliculitis make skin lumps a frequent concern.
English Bulldog: Chronic skin fold infections, folliculitis, and canine acne make bumps a near-constant finding in this breed.
French Bulldog: Atopy-driven folliculitis and histiocytomas are common, and skin folds create additional sites for papule formation.
Pit Bull Terrier: High rates of atopic dermatitis, mast cell tumors, and canine acne make skin bumps a recurring issue.
Pug: Skin fold pyoderma, folliculitis, and mast cell tumors are all overrepresented in this breed.
Boston Terrier: Prone to mast cell tumors and canine acne, with their short coat making any bump immediately visible.
Cocker Spaniel: Susceptible to sebaceous cysts, folliculitis from seborrhea, and lipomas in middle age.
Weimaraner: Known for a higher incidence of mast cell tumors and hypertrophic osteodystrophy-related skin lumps.

How to Evaluate Your Dog's Skin Bumps at Home

A systematic at-home evaluation can provide your vet with useful information. Here is how to assess any new bump:

Document Size, Shape, and Location

Measure the bump (a coin comparison works in photos) and note its exact location. Photograph it in good lighting with a ruler or coin for scale. Is it round or irregular? Flat-topped or dome-shaped? On the surface or under the skin? Record these details because bumps can change between the time you find them and your vet appointment.

Assess Mobility and Firmness

Gently try to move the bump with your fingers. Lipomas are typically soft and freely movable under the skin. Cysts are firm and well-defined. Mast cell tumors can be soft or firm but are often attached to underlying tissue. A fixed, firm mass is more concerning than a soft, mobile one, though exceptions exist in both directions.

Count and Map All Bumps

Run your hands over the entire body, including the limbs, belly, and chest. A single bump has a different significance than dozens of small bumps scattered across the body. Multiple small red papules suggest folliculitis or an allergic reaction. A solitary firm lump in an older dog warrants aspirate cytology regardless of how benign it looks.

Monitor for Changes

If your vet appointment is a few days away, check the bump daily and note any changes in size, color, or texture. A bump that doubles in size over a few days is more concerning than one that remains stable. Take comparison photos daily in the same lighting. Also note whether the bump is itchy, painful when touched, or oozing any discharge.

See your vet urgently if:

A rapidly growing lump that has doubled in size within 1 to 2 weeks
Sudden onset of widespread hives with facial swelling, drooling, or difficulty breathing (potential anaphylaxis, seek emergency care)
A firm, attached mass that cannot be moved freely under the skin
Any lump that is ulcerated, bleeding, or has a crater-like center
Multiple new lumps appearing over a short time period in an older dog
A bump that fluctuates in size, sometimes swelling dramatically then shrinking (classic Darier sign of mast cell tumors)

Treatment and Management

Treatment depends entirely on the type of bump. Here are the most common approaches:

Treating Bacterial Folliculitis

Mild folliculitis responds to topical antimicrobial therapy. A chlorhexidine-based spray applied directly to affected areas can reduce bacterial populations and clear papules without systemic antibiotics. Our Itchy Skin Relief Spray provides convenient daily antimicrobial support. Deep or widespread folliculitis may require oral antibiotics guided by culture and sensitivity testing, ideally for a minimum of 3 to 4 weeks.

Managing Hives and Acute Reactions

Mild hives often resolve with oral antihistamines (diphenhydramine at a veterinary-recommended dose). Severe hives, especially with facial swelling or breathing difficulty, require injectable epinephrine and corticosteroids from an emergency veterinarian. Identifying and avoiding the trigger is the long-term strategy. If hives recur, an allergy workup may be warranted.

Fine-Needle Aspirate for Lumps

For any discrete lump that persists for more than 2 to 3 weeks, fine-needle aspirate (FNA) cytology is the recommended first diagnostic step. A needle is inserted into the mass, cells are collected and examined under a microscope, and in most cases a diagnosis can be made within minutes to days. FNA is quick, minimally invasive, and inexpensive relative to the information it provides.

Surgical Removal

Mast cell tumors, large or problematic lipomas, recurrent cysts, and any mass with suspicious cytology findings are candidates for surgical excision. For mast cell tumors, wide surgical margins (2 to 3 centimeters) are typically recommended. Histopathology of the removed tissue provides a definitive diagnosis and determines whether additional treatment is needed.

Addressing Underlying Allergies

Since folliculitis and recurrent skin bumps are frequently secondary to allergic disease, identifying and managing the underlying allergy is essential for preventing recurrence. Our Dog Skin Condition Checker can help you identify whether allergies might be driving your dog's skin problems.

Red bumps, papules, or irritated skin? Start here.

A topical antimicrobial spray can help clear bacterial folliculitis, reduce secondary infection around skin bumps, and soothe irritated areas while you pursue a diagnosis. Our Itchy Skin Relief Spray contains chlorhexidine and is gentle enough for daily use on bumpy, inflamed skin.

Shop Itchy Skin Relief Spray

Related Conditions

This symptom can be a sign of several underlying conditions. Our in-depth guides cover each one:

Atopic Dermatitis in Dogs, the allergy that most commonly drives recurrent folliculitis and skin bumps
Fungal Skin Infections in Dogs, fungal causes of papules and nodules on the skin
Demodex Mange in Dogs, Demodex mites cause folliculitis that presents as small red bumps
Dog Allergy Testing Guide, identifying the allergy behind recurrent skin bumps
Skin Fold Dermatitis in Dogs, how skin fold infection can present as papules and pustules

Dog Skin Bumps FAQ

Q: How can I tell if a bump on my dog is cancerous?

You cannot reliably tell by looking or feeling. Mast cell tumors, the most common malignant skin tumor in dogs, are known as the great imitator because they can mimic virtually any other type of skin lump. The only reliable way to distinguish benign from malignant is cytology (fine-needle aspirate) or biopsy. Any lump that persists for more than 2 to 3 weeks, grows rapidly, or changes in character should be aspirated.

Q: My dog has small pimple-like bumps all over their belly. What is it?

Small, red, pimple-like bumps on the belly are most commonly bacterial folliculitis, especially if they have tiny white or yellow centers. This is usually secondary to an underlying condition like allergies. Flea bite dermatitis can also produce clusters of small papules on the belly and groin. A vet visit can confirm the diagnosis with impression cytology and help identify the underlying trigger.

Q: Are lipomas dangerous?

Lipomas are benign fatty tumors and are not dangerous in the vast majority of cases. They are the most common soft tissue tumor in dogs. However, they should be confirmed by fine-needle aspirate, because liposarcomas (malignant fatty tumors) can look identical from the outside. Once confirmed as a lipoma, removal is only necessary if the mass is growing large enough to impede movement or comfort.

Q: Why does my dog keep getting bumps in the same area?

Recurrent bumps in the same location usually indicate an ongoing underlying problem. Recurrent folliculitis suggests uncontrolled allergies or a local skin barrier defect. A cyst that keeps refilling was not completely removed or has a persistent blocked duct. Recurring inflammation in a skin fold points to skin fold dermatitis. Identifying and treating the root cause breaks the cycle.

Q: Can I pop my dog's pimples or cysts?

No. Squeezing pustules or cysts can drive bacteria deeper into the tissue, causing a more serious infection (furunculosis or abscess). It is also painful for the dog. If a cyst ruptures on its own, clean the area gently with dilute chlorhexidine and schedule a vet visit. Intentional drainage should only be performed by a veterinarian under appropriate conditions.

Q: My dog got bumps right after a vaccine. Is that normal?

Small, firm lumps at the vaccination site can develop within a few days and usually resolve within 1 to 3 weeks. This is a normal tissue reaction. Widespread hives developing within minutes to hours of vaccination are an allergic reaction and should be reported to your vet immediately. Future vaccine protocols may need to be modified, and pre-treatment with antihistamines may be recommended.

Sources

Hiller A, DeBoer DJ. "The ACVD task force on canine atopic dermatitis (XVII): intradermal testing." Veterinary Immunology and Immunopathology. 2001;81(3-4):289-304.

Blackwood L, Murphy S, Buracco P, et al. "European consensus document on mast cell tumours in dogs and cats." Veterinary and Comparative Oncology. 2012;10(3):e1-e29.

Gross TL, Ihrke PJ, Walder EJ, Affolter VK. Skin Diseases of the Dog and Cat: Clinical and Histopathologic Diagnosis. 2nd ed. Blackwell; 2005.

Loeffler A, Lloyd DH. "What has changed in canine pyoderma? A narrative review." The Veterinary Journal. 2018;235:73-82.

Fulcher RP, Ludwig LL, Bergman PJ, et al. "Evaluation of a two-centimeter lateral surgical margin for excision of grade I and grade II cutaneous mast cell tumors in dogs." JAVMA. 2006;228(2):210-215.