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Allergic Reactions

Although rare, allergic reactions to the clotting factor (called factor) can be life-threatening. They can occur even after having used the factor several times before. You should always be aware of the signs and symptoms of an allergic reaction. A medical provider should be present whenever treatment with a new product is given.

Here are symptoms of an allergic reaction:

  • Itchiness
  • Complaints of tightness in the throat
  • Shortness of breath
  • Headaches
  • Chills
  • Any other unusual symptoms that occur during or shortly following the factor treatment

If clotting factor product is infused too quickly, it may cause flushing, shortness of breath, and nausea. This is not an allergic reaction. Slowing down how fast the factor is given through the vein will prevent these symptoms. One of the reasons why the first clotting factor treatment is given in the hospital or clinic is because the medical staff is trained to recognize allergic reactions and treat them promptly.

If the clotting factor product causes an allergic reaction, you should write down the lot number of the bottles from which the factor came. Do not use any other bottles of factor with the same lot number. Call your HTC immediately to report the reactions.

Fortunately, this does not happen often, but your health care provider should be present whenever treatment with a new product is administered.


As many as one-third of people with hemophilia will develop an antibody (called an inhibitor) to the clotting factor (called factor) product used to treat or prevent bleeding episodes. Developing an inhibitor is the most common and most severe, as well as costly, complication of hemophilia treatment.

The body sees the factor as a foreign substance and tries to destroy it using inhibitors. The inhibitors stop the factor from working, which makes it more difficult to stop a bleeding episode. People with hemophilia who develop an inhibitor do not respond as well to treatment as those who do not develop inhibitors.

Inhibitors most often appear during the first year of treatment, but they can appear at any time.

To learn more about inhibitors, click here.

Treatment Schedules and Dosages

There are different types of treatment schedules that depend mostly on the severity of the bleeding disorder.

  • On-demand treatment (episodic). On-demand treatment (called episodic) is when clotting factor is administered at the time of a bleeding episode (called a bleed). When a bleed occurs, clotting factor should be administered as soon as possible, before any tests, X-rays, scans, etc, are performed
  • Preventive factor treatment (prophylaxis). Prophylaxis is a treatment regimen during which factor is infused several times a week to prevent bleeding. Prophylaxis can help prevent most bleeding episodes. Prophylaxis reduces the number of bleeds but does not prevent all bleeding episodes. The goal of prophylaxis is to raise factor levels to those similar to patients with moderate hemophilia (1% to 5%). MASAC recommends that prophylaxis be considered optimal therapy for individuals with severe hemophilia. There are 2 types of regimens for preventive factor treatments:
    • Primary prophylaxis. Factor is given on a regular schedule not related to bleeding or physical activity. The typical schedule is 2 to 3 times per week, but a health care provider will determine what is right for each person
    • Secondary prophylaxis. Factor is given on a regular schedule for a short time. Secondary prophylaxis is used to help prevent recurrent bleeding or bleeding from a physical activity or medical procedure

Treating early and adequately will help prevent harmful bleeding and damage to joints and vital organs.

Prophylaxis for Adults

  • Prophylaxis has become a standard treatment for children with severe hemophilia. Studies have shown that starting prophylaxis in very young children can prevent or reduce joint damage over the long term by raising clotting factor levels similar to levels found in patients with moderate hemophilia. In fact, MASAC recommends that prophylaxis be considered optimal therapy for children with severe hemophilia
  • You may have questions about prophylaxis if you are an adult. Should you continue prophylaxis if you’ve been receiving it since childhood? Should you start it if you have never received it? Researchers are still studying the use of prophylaxis in adults, although early results have shown that prophylaxis can be beneficial. Talking with your health care provider or HTC team can help you decide whether prophylaxis is a good choice for you

Prophylaxis helps prevent most bleeds, especially into joints and muscles, and pain and joint damage.

Some people with bleeding disorders will still experience a bleeding episode (called breakthrough bleeding) even when they are on prophylaxis treatment.