Reader Question: Spreading Sore Near Dog’s Nipple – What It Could Be and What to Do

by Leticia
(Sundra south africa)

Concern About a Raw, Spreading Sore Near the Nipple

Reader's Question:

Question from Leticia:

Our female dog has a raw sore near her nipple. The sore is getting bigger and spreading down her leg. Lucy’s hair under her front leg is thinning also. Her sore is becoming hard and looks like it's becoming infectious. Anti-bacterial spray does not work.

What the Photos Show and What Might Be Happening

Leticia, thank you for sharing the photos and details. From the images, it appears that Lucy has a large, inflamed, and ulcerated area near her nipple and extending down her leg. The skin looks raw and red, with signs of thickening and possible infection. The fact that it’s spreading and not responding to topical antibacterial spray suggests this is more than a superficial irritation and needs prompt attention.

Possible Causes:

• Mastitis or Mammary Gland Infection: Even in spayed dogs, mammary tissue can sometimes become inflamed or infected, especially if there’s trauma, blocked ducts, or hormonal influence. These infections can become severe quickly and may require oral or injectable antibiotics.
• Skin Fold or Moist Dermatitis (“Hot Spot”): If Lucy has loose skin or friction under her leg, moisture and bacteria can accumulate, leading to a rapidly spreading, painful infection. These often need to be cleaned thoroughly and treated with prescription-strength topical and oral medications.
• Abscess or Deep Skin Infection: The hardness you describe could be a developing abscess beneath the skin. This occurs when bacteria invade deeper tissues, causing swelling and pus formation.
• Mammary Tumor: In some cases, especially in unspayed or older female dogs, sores or firm lumps near
  the nipples can be due to a mammary tumor. These can ulcerate and look similar to an infection.
• Allergic or Autoimmune Skin Reaction: While less likely given the rapid progression, some immune-mediated skin diseases can cause ulceration, hair loss, and thickened, inflamed areas.

What You Should Do:

• See a Veterinarian as Soon as Possible: Because the sore is worsening and spreading, and now feels hard, Lucy likely needs a veterinary exam. Your vet can determine if this is a bacterial infection, abscess, or something more serious like a tumor.
• Antibiotics and Anti-Inflammatory Medication: Topical sprays are not enough for deep infections. Oral or injectable antibiotics are usually required, along with anti-inflammatory medication to reduce pain and swelling.
• Avoid Harsh Cleaning Agents: Don’t use hydrogen peroxide, alcohol, or harsh antiseptics, as they can slow healing. If you need to clean the area gently, use a mild antiseptic solution like diluted chlorhexidine (ask your vet for the correct dilution).
• Prevent Licking or Scratching: Use an e-collar or soft recovery collar to stop Lucy from licking the sore, which can worsen infection and delay healing.
• Monitor for Systemic Signs: If Lucy develops fever, lethargy, loss of appetite, or swelling of nearby lymph nodes, these are signs the infection may be spreading and need immediate veterinary care.

Because the sore is enlarging and hardening, it’s important that Lucy be examined by a vet as soon as possible. Delaying could lead to a deeper infection or systemic illness that becomes much harder to treat.

Please let us know how she does.
Jeff
Editor
Dog Heath Guide

Please note: This information is intended to complement, not replace, the advice of your pet's veterinarian. Always consult a vet for professional medical advice about your pet's health.