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


Lip Curl, Flehmen Response


The vomeronasal organ (Jacobson's Organ) is an "extra" organ for detection of pheromones and other smells found within the nasal cavity of many animal species. It is used mostly for detecting pheromones (chemical messengers carrying information between individuals of the same species) and is important in detecting reproductive hormones in the horse.

The VNO directs certain chemicals directly to the relevant centers in the brain. The flehmen response (upper lip curl) in the horse exposes certain smells directly to the vomeronasal organ.

Healthy horses engage in this behavior in a variety of circumstances. Stallions perform the flehmen response when investigating or detecting a mare in heat. Many horses do this when they are introduced to a strange new taste or smell, especially after they are given oral medication or a new supplement. Some horses do it regularly in association with drinking or playing in water.

Importantly, however, some horses extend their necks and curl their lips when they are in abdominal pain (colic). In rare cases, this can be one of the only signs that the horse is experiencing pain,

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • If you are convinced this is a sign of colic (abdominal pain).
    • If the behavior is persistent and the horse seems to be distressed.
    • 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.
  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If you want to rule out any physical issue being a factor in the behavior.
    • 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.

your role


What To Do

Try to differentiate between this behavior as "normal" (lasting only a minute or two or in response to an obvious outside cause) or as a sign of abdominal pain.

Assess your horse's general health using the Whole Horse Exam (WHE), looking for other abnormalities, especially signs of abdominal pain. Test appetite by offering one small handful of hay. If this behavior continues, worsens or is accompanied by other signs of illness or disease, you will need to call your vet.

What Not To Do

Do not ignore this sign of possible abdominal pain.

your vet's role

Your vet's main concern is to be sure that this behavior is not being caused by a condition causing abdominal pain.
Questions Your Vet Might Ask:
  • Is the horse a mare, gelding or stallion?
  • Are you seeing other signs of abdominal pain (colic)?
  • When did you first notice this?
  • Did you just give the horse an oral medication or wormer?
  • Did the horse just eat or drink something new?
  • Does your horse have a history of colic?
  • What are the results of the Whole Horse Exam (WHE)?
  • Have you changed your horse's feed or management lately?

Diagnoses Your Vet May Consider

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

Very Common
Less Common
more diagnoses

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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further reading & resources

Author: Doug Thal DVM Dipl. ABVP