The causes of colitis include stress, infections (including Salmonella, Clostridium, and E. coli), and parasites (including, Giardia, Cryptosporidium, and whipworms), trauma, allergic colitis, and primary inflammatory bowel disease (lymphoplasmacytic, eosinophilic, granulomatous, and histiocytic types). Colitis may also occur after ingesting contaminated food, being in contact with infected dogs, or after chronic exposure to a wet environment.