Equine recurrent summer dermatitis (ERD): Understanding the mechanisms of recurrence

Introduction

Equine recurrent summer dermatitis (DERE) is a common skin condition in horses, characterized by chronic inflammatory skin reactions. This allergic condition, also known as hypersensitivity to culicoides bites, affects many horses and systematically recurs every year. In this article, we explore the internal and external factors that contribute to these annual recurrences, as well as innovative treatments such as ozonated oil. For a complete guide on dermatitis, see our article on equine summer dermatitis.

Structure and Function of Equine Skin

Equine skin is composed of three layers: the epidermis (protective barrier, slightly thinner than in humans), the dermis (thicker, containing more nerve receptors — which explains the horse's exceptional sensitivity to bites) and the hypodermis (adipose tissue, thermal insulator). In horses suffering from DERE, the epidermal barrier can be compromised, facilitating the penetration of allergens.

Factors Contributing to Annual Recurrences

Internal Factors

• Genetic predisposition: some breeds are more susceptible (Icelandic up to 50%, Friesian, Arabian Thoroughbreds, Welsh ponies)
• Immune dysregulation: Th1/Th2 imbalance, excessive IgE production, amplified inflammatory reaction
• Impaired skin barrier: vicious circle of scratching → damaged epidermis → easier penetration of allergens
• Progressive increased sensitization: each episode lowers the trigger threshold and worsens future reactions

External Factors

• Seasonality: DERE more frequent between March and October, peak culicoides activity period
• Environment: proximity to water sources, humid areas, lack of shelter, evening pastures
• Stress: changes in environment, changes in social group, unbalanced diet

The Benefits of Ozonated Oil in the Treatment of DERE

OZONE SOIN PEAU has proven to be a promising treatment for DERE thanks to its multiple properties:

• Antimicrobial: prevents secondary infections (staphylococci, fungi) that occur when the horse scratches
• Anti-inflammatory: reduces edema, redness and inflammatory mediators
• Healing: stimulates collagen production and restores the epidermal barrier
• Soothing: reduces intense itching, breaks the itch-scratch-lesion vicious cycle
• Regenerating: promotes cell renewal and strengthens the skin barrier
• Natural and safe: alternative to corticosteroids, can be used long-term

Usage Protocol

For prevention (from March-April): apply OZONE SOIN PEAU 2-3 times/week to sensitive areas (mane, tail, withers, belly). Gently massage to absorb.

For treatment (DERE flare-up): gently clean affected areas, apply 1-2 times/day until complete improvement, then continue with prevention.

Conclusion: A Global Approach to Managing DERE

Recurrent summer dermatitis is a complex condition requiring long-term management. A global approach combines environmental management (limiting exposure to culicoides), physical protection (insect-repellent blankets, shelters), innovative topical treatments, and nutritional support. OZONE SOIN PEAU integrates perfectly into this global strategy thanks to its antimicrobial, anti-inflammatory, healing, and soothing properties.