Guide to Summer Skin Fungus

What Is Summer Skin Fungus?

Summer skin fungus in horses refers to a group of fungal or fungal-like skin infections that commonly flare up in warm, humid weather. These infections may involve true fungi (like dermatophytes, which cause ringworm) or opportunistic organisms like dermatophilus (which causes rain rot). Summer conditions promote moisture retention on the skin, creating a perfect environment for fungal growth.

Common Types of Summer Skin Fungus

• Rain rot (Dermatophilosis): Caused by Dermatophilus congolensis; appears as crusty scabs with matted hair.

• Ringworm (Dermatophytosis): Caused by fungi such as Trichophyton or Microsporum species; appears as round, hairless lesions.

• Cannon crud (Fungal pastern dermatitis): Often found on the cannon bones; scaly, crusty skin with patchy hair loss.

Symptoms

• Hair loss in circular or irregular patches

• Crusty, scabby skin, sometimes with pus

• Raised bumps or tufts of hair that pull out easily

• Flaky or greasy skin, especially on legs, back, or neck

• Itching or sensitivity to touch

• Spread of lesions across the body during wet or humid conditions

Causes and Risk Factors

• Humidity and sweat accumulation

• Frequent hosing or sweating without proper drying

• Poor grooming or sharing contaminated tack/grooming tools

• Compromised skin from insect bites or abrasions

• Weak immune function

Diagnosis

Veterinary diagnosis may include:

• Visual examination

• Skin scraping or culture (to identify fungi or bacteria)

• Microscopic evaluation of hair and scabs

Treatment Plan

1. Isolate the Horse (If Ringworm Is Suspected)

Ringworm is contagious to other horses and humans. Use separate tack, grooming tools, and turnout if ringworm is suspected.

2. Clean the Affected Area

• Clip hair around lesions to improve air exposure.

• Gentle washing - antibacterials (e.g., iodine-based, chlorhexidine solutions, or miconazole) may be used. Wet area with warm, clean water, apply solution and rub gently, let sit on skin for 5 mins before rinsing well.

• Rinse thoroughly and dry completely—fungus thrives in moisture. Save your old bath towels!

3. Apply Topical Treatments

• Use veterinarian-approved antifungal creams or sprays

• Specifics

  • Rain rot - appears as crusty scabs with matted hair anywhere on body - we like to use Betadine soap scrub or chlorhexidine solutions let sit for 5 mins before rinsing, then after drying MTG which also helps soften scabs, and treat fungus. *** BE CAREFUL in summer as this is an oil based treatment and can result in sunburn ***

  • Ringworm - appears as round, hairless lesions - we like to use either clotrimazole (Lotrimin AF), terbinafine (Lamisil AT) cream, and Desenex Antifungal Powder With 2% Miconazole Nitrate. We apply the cream to clean dry lesion, then powder on top. I feel it helps stop spreading. WASH YOUR HANDS you will get it too!

  • Cannon crud (Fungal pastern dermatitis): Often found on the cannon bones; scaly, crusty skin with patchy hair loss. we like Bev’s Equine Magic Salve mixed with Vaseline for legs. The Vaseline helps it stick and softens the scabs, the salve is sulfur based and kills fungus.

• Other things that we find very affective - Remove loose scabs gently; do not pick or irritate the skin further. We LOVE zinc oxide baby butt paste to help soften the scabs, protect the skin and make scab removal easy on your horse. We also LOVE cornstarch no perfume baby powder - once the scabs are off the fungus is usually dead. Corn starch helps absorb any moisture and flies hate baby power so a win-win

• HEAL SHIELD SHORTY boots are great for keeping pasterns and coronet bands covered - keeps ointment and medication in place while softening scabs and baby powder to help allow skin to heal. As the scabs loosen and are removed, don’t forget to keep any open sores covered to prevent summer sores! For airdrying try HEAL SHIELD line of Fly-Go boots.

4. Systemic Treatment (For Severe Cases)

• Your vet may prescribe:

• Oral antifungals (e.g., griseofulvin, terbinafine)

• Antibiotics (if secondary bacterial infection is present)

• Anti-inflammatories to reduce itching and discomfort

Environmental Management

• Disinfect grooming tools, tack, and wash racks after every use.

• Clean and sun-dry blankets, saddle pads, and brushes. Fly sheets and fly masks should be washed frequently - ideally changes daily (two fly-sheets are better than one in the summer).

• Improve ventilation and hygiene in stalls and barns.

• Avoid sharing equipment between horses.

Prevention Tips

• Dry horses thoroughly after bathing or heavy sweating. sponge legs, use sweat scraper, then towel dry legs and bellies - no dripping legs or bellies, Don’t forget to towel dry their faces too.

• Maintain good grooming practices and check skin regularly. gentle curry daily with curry comb or mitt can help you find any scabby patches early and treat before they spread.

• Rotate or clean turnout areas to prevent overly muddy or wet conditions.

• Avoid blanketing in hot, humid weather unless necessary.

• Use sweat-absorbing saddle pads and breathable gear. Always bathe or sponge sweaty areas. Wash saddle pads after every use.

When to Call the Vet

• Lesions spread or worsen despite treatment

• The horse is in significant discomfort or starts itching excessively

• You suspect ringworm or another contagious infection

• There is swelling, pus, or signs of systemic illness

Conclusion

Summer skin fungus can be frustrating but is highly treatable with prompt, diligent care. Cleanliness, dryness, and consistent treatment are key. Early intervention can prevent spread to other horses and help your horse stay comfortable and healthy throughout the hot season. ALWAYS consult your veterinarian