If your horse comes in from grazing with a swollen throat, don’t panic. It could be the result of Grass Glands.
Enlarged submandibular lymph nodes (the area at the back of the throat, behind the jawbone) are a common event in horses. Frequently, a horse or pony will be brought in from the field after grazing for some hours with large, firm and usually painless swellings in the area where the throat latch would go. Occasionally, the swelling will be accompanied by fluid under the skin.
Affected horses can look rather like hamsters and may be reluctant to work with their head down on the bit. Such lumps are commonly mistaken for a manifestation of the disease Strangles, when in fact they are simply swellings of the parotid salivary glands.
Such swollen glands can vary in size from day to day. They are often linked with particular areas of grazing and are suspected to be a form of allergic reaction .
The glands enlarge after the horse has been out at grass and most return to normal size within 36 hours with no treatment. It helps if such horses, when affected, are fed from a height once they are brought in, to allow any accumulation of fluid to drain.
There is no need to do anything except have a careful feel of the area to confirm it is just swollen parotid glands. Continued enlargement or involvement in surrounding tissues suggest it may be abscessing , also a fairly common event in horses. If other symptoms like not eating, nasal discharge, lethargy, or pain occur, a vet should be consulted.