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


Lip Quivering, Lip Flapping, Strange Movement of Lips


Some horses make strange lip movements seemingly just for fun. However, lip movements can also be indicative of a wide variety of emotional states and can even signal a physical problem.

Like lip curl (Flehmen Response), a variety of other lip movements can be considered normal behavior or can be a sign of a physical pain, or anxiety or irritation.

Lip twitching and trembling can be related or unrelated to eating. Occasionally, a horse's lips will move in a strange or inappropriate way when they are offered feed. These horses may also not be able to properly grasp feed with their lips and move it back in the mouth. This is a classic finding in horses with Yellow Star Thistle or Russian Knapweed poisoning.

Foreign objects embedded in the mouth and dental issues can cause strange lip movements out of discomfort.

Lip twitching and flapping are common after a horse has been given an oral medication or de-wormer. The lip curl (Flehmen response) is a natural gesture when a horse is presented with a new smell, and is common in breeding stallions around mares. I wrote another record dedicated to the lip curl.

Some horses flap their lips loudly when they are nervous or anxious, or anticipating an undesirable event.

Recognize that a variety of lip movements can be considered normal, but that they might also signal anxiety or even a physical problem.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • 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 the behavior continues with no explanation.
    • If the horse's appetite and attitude are normal and you see nothing else wrong.
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.
You also might be observing
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Less Common
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your role


What To Do

Carefully observe the horse for a few minutes before making any assumptions about what is going on. Is this trembling, smacking, or something else. Take a video and share with your vet.

Consider the context. When is this occurring? Is it under saddle, when fed, or when simply resting.

When horses twitch or flap their lips under saddle, it can indicate stress. Consider the factors that might be causing anxiety or irritability, and adjust your approach accordingly.

If the lips movements are occurring when the horse is fed, determine whether or not the horse can properly eat. Assess your horse's general health using the Whole Horse Exam (WHE) paying particular attention to how the horse moves at the walk, and their attitude and appetite, heart rate and rectal temperature. Assess the mouth (wear gloves), and look at the inside and outside of the lips and look in the nostrils. Offer feed and water and determine whether they are interested in feed and can chew and swallow. Look carefully for trembling elsewhere on the body. Contact your vet with your findings and concerns.

your vet's role

Your vet will assess the behavior to determine whether or not it is normal for the horse. They will perform a physical exam, paying particular attention to the mouth and neurologic system. Depending on the characteristics of the behavior, they may want to rule out intestinal conditions causing colic.
Questions Your Vet Might Ask:
  • Does the horse seem normal otherwise?
  • When do you see the behavior exhibited?
  • Are you seeing other signs of abdominal pain (colic)?
  • Is this a long standing behavior or something new?
  • Did you just give the horse an oral medication or wormer?
  • Does the horse seem to be having difficulty eating or dropping feed?
  • How frequent are you noticing the behavior?
  • Does the horse's behavior seem normal otherwise?
  • Do you notice other behavioral changes?
  • When was the horse's last dental exam by a vet or dental tech working with a vet?
  • Do you notice any signs of abdominal pain (colic)?
  • What are the results of the Whole Horse Exam (WHE)?
  • What were the findings on the dental exam?

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)

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Author: Doug Thal DVM Dipl. ABVP