Final answer:
Sheep are less commonly affected by flea allergic dermatitis in the UK than other domestic animals due to their dense wool and typical management conditions which lessen flea infestation.
Step-by-step explanation:
Flea allergic dermatitis is a common condition in pets caused by hypersensitivity to flea bites. It is a type of allergy or hypersensitivity reaction and is less commonly seen in sheep among the options provided. In the UK, pets like cats and dogs are more frequently affected by flea allergic dermatitis due to their closer proximity with environments where fleas can thrive. Horses, guinea pigs, and rabbits can also be affected, but sheep have their own protective measures such as dense wool that can provide some barrier against flea infestations. Moreover, their typical management and housing conditions contribute to the lower prevalence of flea allergic dermatitis in this species.