What you see. The starting point for addressing any equine health related issue is your observation.


Swelling of Jaw or Under Jaw


Trauma to a horse's face that results in a swollen lower jaw is common. Kicks from other horses can result in a fractured jaw or severe bruising, either of which can cause swelling and difficulty chewing. Dental conditions like abscessed molars (cheek teeth) can also result in swelling of the lower jaw and overlying muscles.

Strangles, a highly contagious disease caused by Streptococcus equi, often appears as severe swelling usually behind or under the jaw in the space between the two bones of the jaw. This is often accompanied by a fever, nasal discharge and cough.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • If the horse has no appetite and is obviously depressed.
    • If the results of the Whole Horse Exam (WHE) in the resting horse indicate fever (Temp >101F/38.3C) or heart rate greater than 48 BPM.
    • If the horse seems to be having difficulty eating, in addition to showing this sign.
  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If this is the only sign you notice. The horse seems well to you otherwise.
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.
    • If the swelling is mild or moderate, and not increasing rapidly.
You also might be observing
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your role


What To Do

Until your vet arrives, if the cause of the swelling is unknown, treat the horse as contagious and isolate it. Wear rubber gloves to prevent transmission to other horses. Most swellings here that are caused by infection are accompanied by a fever.

Assess your horse's general health using the Whole Horse Exam (WHE), paying particular attention to whether the horse has a fever- a rectal temperature > 101F. Assess the area of concern wearing gloves due to the possibility of Strangles.

When assessing this area, keep in mind that the lower jaw, like yours, consists of two bones that are joined at the chin. Between those two sides of the mandible lies the floor of the mouth, lymph nodes, salivary glands and a variety of other structures. On the outside of each of the jawbones lies a heavy, thick sheet of muscle (the masseter) involved in chewing. Injury or infection of these structures can cause swelling .

Contact your vet with your findings and concerns.

your vet's role

Your vet will try to determine whether the swelling is a traumatic injury or a contagious infection that might affect other horses.
Questions Your Vet Might Ask:
  • Does the horse have an appetite?
  • Can you see drainage or a wound?
  • What are the results of the Whole Horse Exam (WHE)?
  • What is the horse's rectal temperature?
  • Is the horse pastured with other horses?
  • Can the horse chew normally?
  • How old is the horse?

Diagnoses Your Vet May Consider

The cause of the problem. These are conditions or ailments that are the cause of the observations you make.

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Treatments Your Vet May Recommend

A way to resolve the condition or diagnosis. Resolving the underlying cause or treating the signs of disease (symptomatic treatment)

Very Common
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Author: Doug Thal DVM Dipl. ABVP