Health Guide

Cat hair extract (By injection)

Cat Hair Extract (kat hare-EX-trakt)

Used to test for allergy to cats and treats symptoms of allergy to cats.

Brand Name(s):

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not receive this medicine if your skin test shows that you are either severely allergic to cats or not allergic to cats. You should not receive this medicine if you have an autoimmune disease or a bleeding disorder.

How to Use This Medicine:


  • Your doctor will prescribe your exact dose and tell you how often it should be given. This medicine is given as a shot under your skin.
  • A nurse or other health provider will give you this medicine.
  • Any reaction to your skin test should appear about 20 minutes after your shot. Some reactions may appear later. Your doctor or caregiver will watch you for signs of allergy for at least 30 minutes after your shot.
  • If you receive this medicine to treat a confirmed allergy, you will need to have a shot every 1 to 4 weeks. Be sure to keep all appointments.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some medicines can affect how cat hair extract works. Tell your doctor if you are also taking any of the following:
    • Allergy medicine, such as cetirizine, loratadine, or terfenadine
    • Blood pressure medicine
    • Topical steroid medicine, such as hydrocortisone
    • Tricyclic antidepressants

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have heart disease.
  • Tell your doctor if you have asthma, fever, or flu symptoms, or if you have recently been exposed to cat hair.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Lightheadedness or fainting

If you notice these less serious side effects, talk with your doctor:

  • Dizziness, weakness, or muscle cramps
  • Nausea, vomiting, diarrhea, or stomach pain
  • Pain, itching, tenderness, or swelling where the shot was given
  • Runny or stuffy nose

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 7/4/2018
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