Horses are social animals. Since horses are also prey animals, they have adopted sociality as a behavioural strategy – the benefits of sticking together outweigh the disadvantages . For instance, in the wild, horses must identify predators immediately. However, constant surveillance of their surroundings means that there is less time for eating. Therefore, horses that are in a herd can share vigilance and increase their feeding time. Herd life has resulted in ritualised interactions such as allogrooming . Horses can recognise, remember and understand relationships and social status within the herd and can form long-lasting relationships with other horses .
Allogrooming is “a form of caregiving through physical contact, typically where one animal uses its hands, mouth or another part of its body to touch another animal” . Many animals use this technique, including primates, birds, rodents, arthropods and, of course, ungulates . There are many varied benefits and reasons why animals use allogrooming however, it is usually for hygienic reasons or social benefit .
There have been several recent studies that suggest that allogrooming reduces stress within the horse. In 1993, Feh and De Maziѐres  found that the imitation of grooming at the horse’s preferred site significantly reduced their heart rate, indicating a reduction in stress levels. The heart rates were reduced on average by 11.4% for adults and 13.5% for foals  . A 2004 study  also demonstrated similar results. They found that horses during a massage experienced a significant reduction in heart rate, which was more significant when massage techniques were applied to allogrooming sites . Allogrooming was also found to be effective for stress relief in other species, such as primates, dogs, and cattle .
Many studies have concluded that the most effective allogrooming site is at the wither. Thorbergson et al  found that scratching the wither area for one minute will increase relaxation when the horse is under saddle. Other areas on the horse may be used for allogrooming, such as the hip and shoulder, though they are less effective .
Allogrooming is an important aspect of a horse’s wellbeing while also improving the horse/rider relationship. Equine Scientist Andrew McLean suggests that performing allogrooming with your horse can assist in forming and maintaining a strong relationship .
 Dierendonck, M 2006, The Importance of Social Relationships in Horses, Utrecht University
 Henderson, A 2018, ‘Keeping in Touch: Why horses nibble on each other’s withers or necks’, Horse Canada, July/August, pp. 40-41
 Russel, I 2018, ‘Allogrooming’, in Encyclopaedia of Animal Cognition and Behaviour, in J. Vonk & T.K Shackelford (eds.), Springer International Publishing
 Feh, C & De Maziѐres, J 1993, ‘Grooming at a Preferred Site Reduces Heart Rate in Horses’, Animal Behaviour, vol. 46, pp. 1191-1194
 McBride, S, Hemmings, A & Robinson, K 2004, ‘A Preliminary Study on the Effect of Massage to Reduce Stress in the Horse’, Journal of Equine Veterinary Science, vol. 24, no. 2, pp. 76 – 81
 Normando, S, Haverbeke, A, Meers, L, Ӧdberg, F.O, Ibáñez Talegón, M & Bono G 2003, ‘Effect of manual imitation of grooming on riding horse’s heart rate in different environmental situations’, Veterinary Research Communications, vol. 27, pp. 615-617
 Thorbergson, Z, Neilson, S, Beaulieu, R & Doyle, R 2016, ‘Physiological and behavioural responses of horses to wither scratching and patting the neck under saddle’, Journal of Applied Animal Welfare Science, vol. 19, no. 3, pp. 245-259