| Name | Etiology | Signs - Lesions | Comments |
| Actinobacillus suis infection | Actinobacillus suis | Unusual but in feeding/finishing and mature swine, the lesions are raised, red and rhomboid. | Signs, internal and cutaneous lesions can (rarely) resemble those of acute erysipelas |
| Aural hematoma | Trauma to ear followed by hemorrhage between skin and cartilage | Thickening and inflammation of ear over organizing hematoma. Lesions can be very large. | Trauma from many causes: bites, violent head shaking, commingling. |
| Dermatosis vegetans | Semi-lethal hereditary defect affecting occasional pigs. | Coronary band lesion on one or more feet of neonate, which leads to hoof deformity. Red macules expand, become papillomatous. | Defect originally in Landrace breed. Most affected piglets die within a few weeks. Many survivors have interstitial pneumonia. |
| Epitheliogenesis imperfecta | Congenital defect | Missing areas of skin since birth, often over back or rump, perhaps mouth. | Small lesions often heal by scarring. |
| Erysipelothrix rhusiopathiae | Acute: Raised, rhomboid lesions. Chronic: Peeling plaques often over back. Necrosis of parts of ears, tail. |
Acute skin lesions often resolve if animal recovers promptly. Skin lesions appear slightly after acute febrile stage of disease. | |
| Greasy pig disease | Staphylococcus hyicus skin infection | Brownish lesions in axilla and groin spread to head, face, other areas, perhaps mouth. Lesions dark, greasy, often extensive. | Triggering factors are poorly understood. Irritation of skin may precede the infection. Treatment seldom is satisfactory. |
| Necrotic ear syndrome | Trauma, vasculitis, often bites, and secondary infection. | Areas of ulceration, infection and necrosis in ear(s). | Infection occasionally results in septicemia and death. |
| Pediculosis (lice) | Haematopinus suis louse. | Rubbing, scratching, anemia. Eggs attached to hair on jowls, flanks, inner surface of legs, behind ears. | Leads to unthriftiness and anemia. Lice sometimes transmit pox virus. |
| Photodynamic dermatitis | Photodynamic agents (plants or drugs) plus sunlight. | White areas of skin inflamed and pruritic. Severe peeling of areas of necrotic skin. | Many plants and drugs are photodynamic. Conjunctivitis often accompanies the dermatitis. |
| Pityriasis rosea | Unknown but some evidence of hereditary predisposition. | Raised, expanding circular lesions in 12-14 week old pigs. Lesions usually on ventral abdomen, less often elsewhere. | Lesions resolve within a few weeks without treatment. Disease may go unnoticed unless ventrum is examined. |
| Porcine dermatopathy and nephropathy syndrome (PDNS) | Mechanism unknown but associated with post-viral (PCV2, PRRSV, CSF)* infection, perhaps an immune mediated disease | Red to purple, circular 1 cm lesions appear on perineal, ham, ventral regions that may enlarge and coalesce. Nephropathy also present may lead to death in days to weeks. | Diagnosis by recognition and histopathology on skin and kidney. Usually sporadic but morbidity can approach 10%. No treatment. |
| Pox | Swine pox virus | Initial 1-2 cm round to oval lesions on ventrum but can extend over the body. Papule, vesicle, pustule and scab stages. | All age groups susceptible. Usually seen in young, growing pigs. Pox virus sometimes transmitted by lice. Congenital pox occurs sporadically. |
| Pustular dermatitis | Lancefield type C Streptococci | Pustules on posterioventral abdomen, inguinal area, inner thighs, perhaps eyes, lips, ears. Pustules rupture, are replaced by black scabs. | Most pigs recover in a few weeks. Provide clean bedding, improve sanitation. Recovery perhaps hastened by antibiotics in water or feed. |
| Ringworm | Usually Microsporum nanumor Trichophyton verrucosum. | Roughly circular, expanding hairless areas that develop crested scabs. Non-pruritic. | Usually self-limiting. Contagious to humans. Occasionally caused by other fungi. Usually seen in old swine and quite common in sows. |
| Skin necrosis of piglets | Skin abrasion with secondary infection. | Abrasive lesions on knees, fetlocks, coronets, hocks, or elbows lead to septicemia; often high mortality. | Lesions often are more serious than realized. Less abrasive surfaces or adequate bedding are necessities. |
| Sunburn | Excessive sunshine on skin | Pigs may “drop to belly” from pain on sunburned back. Reddening, thickening, peeling of most exposed skin, usually on back and ears. Unpigmented skin more susceptible. | If shade is provided, pigs will not lay in the sun. |
| Vesiculating viral diseases | Foot-and-mouth disease (FMD), Vesicular stomatitis (VS), Vesicular exanthema(VE). | Round to oval vesicles on feet, in and around the mouth, on snout, in nostrils, occasionally elsewhere. | Lesions similar in all vesiculating viral diseases and cannot be used to differentiate. Report all promptly! |
| Vices | Tail or flank biting; savaging of moribund swine. | Tail or flank bite wounds. Moribund swine often have red, linear bite marks. | Overcrowding and idleness are thought to contribute to development of vices. |
Key:
CSF - classical swine fever
PCV2 - porcine circovirus type 2
PRRSV - porcine reproductive and respiratory syndrome virus