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Bleeding disorders: Allergic reaction to factor

What is an allergic reaction to Factor?

Patients who have hemophilia and receive factor concentrate may have allergic reactions to the factor concentrate. These reactions are very uncommon and if they do happen they usually occur within the first 20 doses of factor. The reactions usually happen as the factor is being given or after. Be aware possible reactions and what to do if they occur.

What causes a reaction to Factor?

It is not known why reactions to factor occur. It is more common in Factor IX than Factor VIII.

How should I care for my child?

Mild symptoms What to do:
Hives*, itchy, stuffy, runny nose, coughing, fever Stop giving Factor. Give a dose of diphenhydramine (Benadryl). Call the hematology clinic. Other medication may be prescribed. 
Moderate symptoms What to do:
Hives* on a large part of the body, intense itching, swelling of lips or eyelids.   Stop giving Factor. Give a does of diphenhydramine (Benadryl). Call the hematology clinic. Stay with your child in case it gets worse. 
Severe symptoms What to do:
Tightness in the throat or chest, shortness of breath, chest pain, wheezing, swelling of face, paleness, dizziness, fainting, hives, swelling of lips or eyelids.  Stop giving Factor. Call 911 first, give a shot of epinephrine (EpiPen®) into thigh, call the hematology clinic. 

*Hives are round red welts on skin. It is the most common symptom that occurs.

Check with your hematology health care provider for exact drug dosages and directions.

Epinephrine (EpiPen® EpiPen Jr®)


Prednisolone Liquid 3 mg/ml


Prednisolone Tablets


Diphenhydramine (Benadryl) Liquid


Diphenhydramine (Benadryl) 12.5 mg chewable tablets


Diphenhydramine (Benadryl) 25 mg capsules

Keep diphenhydramine (Benadryl) in the home for emergency use. Children 5 years and older who have a history of allergic reaction should also keep epinephrine with them.


This information is not specific to your child, but provides general information. For more information, please call your helath care professional.

Reviewed 7/2017

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This page is not specific to your child, but provides general information on the topic above. If you have any questions, please call your clinic. For more reading material about this and other health topics, please call or visit Children's Minnesota Family Resource Center library, or visit

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