My horse has allergies or immune issues

Immune System & Allergies

Allergic reactions, recurring infections, constant sensitivity — the immune system is closely connected.

Skin & Coat

Itching, rubbing, bald patches, flaky or inflamed skin — skin issues are rarely just skin.

Respiratory

Coughing, poor air, dust sensitivity — respiratory topics are closely tied to management and the immune system.

An acute cough is a symptom of suddenly arising airway irritation, often as part of a viral or bacterial infection of the upper and lower airways. It can be harmless and brief, but with fever, breathing difficulty or impaired general condition it may indicate a more serious infection and is often contagious in the stable.

Anaphylaxis is an acute, generalised allergic overreaction of the immune system (usually IgE-mediated) with massive histamine release. Within minutes it can threaten circulation and breathing and is a life-threatening emergency. Typical triggers are injections (medicines, vaccines, sera), insect stings or, more rarely, feed components.

Chronically progressive disorder of the lymph drainage in the lower legs of heavily feathered breeds (among others Shire, Clydesdale, Belgian Draught, Tinker). There is increasing swelling, skin folds and nodule formation under the dense feathering; a hereditary predisposition for a disturbed elastin/connective tissue regulation is assumed. CPL is not curable but can be slowed by consistent management.

In DDSP, the rear edge of the soft palate displaces over the epiglottis and temporarily obstructs the airways, especially at fast work. Typical is a gurgling breathing sound on exhalation with a sudden drop in performance; many horses start normally and only break down at high speed.

Chronic inflammatory airway disease caused by dust/mould allergens, with bronchospasm and increased mucus.

Sarcoids are the most common skin tumours in horses — locally aggressive, fibroblastic skin growths associated with bovine papillomavirus (BPV-1/-2). They do not metastasise but tend to recur and can become more aggressive after irritation.

In EIPH, bleeding from small lung vessels into the airways occurs under high exertion, triggered by very high pressures in the pulmonary capillaries during intense work. It mainly affects racehorses and high-performance horses and often goes unnoticed, as only some horses show visible nosebleeds.

In a true feed allergy, the immune system reacts to a feed component, usually with skin or digestive symptoms. In horses, however, it is rare and often overdiagnosed — many supposed allergies are non-immunological intolerances or have other causes. Proof is demanding and best achieved through a controlled elimination diet.

Hereditary connective tissue disorder of the skin (collagen defect through a mutation in the PPIB gene), in which the skin layers are insufficiently anchored. HERDA is inherited autosomal-recessive and occurs above all in certain cutting/performance lines of the Quarter Horse; only homozygous animals are affected, carriers are clinically unremarkable.

Acute, often allergic or pseudo-allergic skin reaction with suddenly appearing raised wheals. Can be harmless and transient but may recur — and is a warning sign with accompanying swelling or breathing difficulty.

Lymphangitis is a painful inflammation of the lymph vessels and surrounding tissue, usually in one hind leg, with marked swelling. Triggers are often bacterial infections via small skin lesions (e.g. with mud fever), more rarely non-infectious/immune-mediated processes. It runs acutely, is very painful and tends to recur.

Skin disease caused by parasitic mites (often Chorioptes on the pastern/lower leg, less often Sarcoptes/Psoroptes) with intense itching, scaling and crusts. Mange is contagious and often transmitted via contact or shared equipment.

Umbrella term for an inflammatory skin reaction in the pastern fold with weeping, crusty or fissured areas. Usually multifactorial (wet, dirt, friction) and can be complicated by bacteria or mites.

Pemphigus foliaceus is the most common autoimmune skin disease of the horse. The immune system forms antibodies against connecting proteins of its own epidermal cells, so that skin layers detach and pustules, crusts and scales form. The changes often start on the head, legs or lower abdomen and can spread.

In photosensitisation, the skin overreacts to sunlight because light-active substances (photosensitisers) in the skin release UV energy and damage tissue. Mainly unpigmented, white skin areas are affected. A primary form (photosensitisers directly from plants) is distinguished from a secondary, liver-associated form, in which a damaged liver no longer sufficiently excretes a chlorophyll breakdown product (phylloerythrin).

Pleuropneumonia is a severe bacterial infection of the lung and pleura, in which inflammation and fluid/pus accumulate in the chest cavity. It often occurs after long transports with a fixed, raised head (shipping fever) and is a potentially life-threatening disease that must be treated quickly by a vet.

Purpura haemorrhagica is an immune-mediated, necrotising inflammation of small blood vessels (type III hypersensitivity). It classically appears about two to four weeks after a strangles infection (Streptococcus equi) or, more rarely, after vaccination/other infections, when the immune system damages the vessel walls with cross-reacting complexes. Typical are extensive oedema and pinpoint mucosal bleeding.

Bacterial skin infection caused by Dermatophilus congolensis that flares up with persistent wetness. Typical are crusty, paintbrush-like matted hair tufts along the topline; bald patches appear after the crusts come off.

Contagious fungal infection of the upper skin layers (usually Trichophyton/Microsporum) with circular, scaly, hairless patches. Highly contagious between horses and transmissible to humans (zoonosis).

In roaring, the nerve supply to the laryngeal muscles — usually on the left side — is impaired, so that a vocal-fold cartilage does not open sufficiently on inhalation. This narrows the airways under exertion and produces the typical whistling breathing sound; large horses are especially affected.

Hereditary, severe defect of the immune defence in the Arabian foal: through a mutation in the DNA-PKcs gene (PRKDC) functional B and T lymphocytes are not formed. SCID is inherited autosomal-recessive; affected foals are practically defenceless against infections after the maternal antibodies from the colostrum are used up. The disease is not curable, affected foals usually die in the first months of life.

In sinusitis, one or more of the air-filled paranasal sinuses become inflamed, often with an accumulation of secretion or pus. It arises primarily after airway infections or secondarily through diseased cheek-tooth roots whose tips reach into the maxillary sinus.

Allergic skin reaction (hypersensitivity to the saliva of biting midges) with intense itching, mainly at the mane crest and tail base.

Hereditary connective tissue disorder of the Warmblood through a mutation in the PLOD1 gene (disturbed collagen cross-linking), inherited autosomal-recessive. Affected homozygous foetuses are mostly aborted or come into the world with extremely vulnerable, tearing skin and overextensible joints; the form is regarded as predominantly lethal. Carriers are clinically unremarkable and relatively frequent in Warmbloods.