The skin is the largest organ of the body, and conditions affecting it can be uncomfortable for the horse and impact its ability to be ridden. Conditions broadly fall into one of 3 groups;  Infections, Skin Tumours and Reactive Skin Disease :

Infections include mud fever (Bacterial), Papilloma & other warts (Viral),   Ringworm (Fungal) and Parasitic including mites, ticks and a variety of flies

Reactive Skin Disease  include  Allergic,  Auto-immune and Photo-sensitisation such as sunburn and reaction to certain plants – Phytophototropism

Skin Tumours include Sarcoids, Melanomas and Squamous Cell Carcinoma

Climate change is increasing the impact of some of these conditions, with changing fly populations and increasing incidence of sun burn