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Overview: Transfer factor is a dietary supplement made from small proteins (peptides) from white blood cells, cow milk, or other animal sources. It is available as an over-the-counter supplement, usually in capsule or tablet form. People take transfer factors for many reasons, such as immune system support, infections, and cancer, although its benefits are not well defined. Transfer factors seem to be well tolerated, but there is not enough research to know what the side effects may be. Check with your health care provider before taking transfer factors, especially if you have any health conditions or take any medicines.

Uses

What is transfer factor used for?

Transfer factor is used for various reasons, although its benefits are not well defined. Some common reasons people may take transfer factors include the following.

There is not enough research in humans to know if transfer factor has benefits for any use. If you have a concern listed above (especially an infection, immune deficiency, or cancer), do not use dietary supplements to delay or replace medical care. Talk to a health care provider about your treatment options.

Note: The Food and Drug Administration (FDA) has not reviewed transfer factor supplements for safety and effectiveness, and it is not approved by the FDA. Learn more about dietary supplements here.

How does transfer factor work (mechanism of action)?

Transfer factor refers to small proteins (peptides) that were discovered in the 1950s. Scientists found that these small proteins, taken from the white blood cells of a person who had immunity to a certain infection, could transfer that immunity to another person who did not have it. Transfer factor is also sometimes called dialyzable leukocyte extract (DLE), which is an older medical name for these proteins.

Today, most transfer factor dietary supplements are made from cow colostrum (the first milk produced after a calf is born), pig spleen tissue, or egg yolk. These animal-derived products contain small proteins that are thought to help the immune system recognize and respond to germs or threats.

Transfer factor may work by supporting the part of the immune system known as cell-mediated immunity. This is the part of the immune system that uses specialized white blood cells, rather than antibodies, to fight infections. Transfer factors may help the body by affecting certain chemical signals (called cytokines) that control how the immune system responds to infections and other threats. It may also help reduce certain signals that promote inflammation.

Small human studies of transfer factors suggest possible benefits for some uses, such as chronic fatigue syndrome and herpes infections, including shingles. However, the specific active ingredient in transfer factor products has not been clearly identified. Because transfer factor contains a complex mixture of many different molecules, it is hard for scientists to know exactly how these supplements affect the body. Transfer factor has also been studied for potential anti-cancer effects, but it is not proven to prevent or treat cancer in humans.

Transfer factor products are made from animal tissues and naturally contain many different proteins and other substances. The amounts of each substance in a specific transfer factor product may vary from product to product. Some, none, or all of these substances may have effects on the body. These effects may change depending on how much of each substance is found in the product you are using.

How should I store transfer factor?

You should store transfer factor according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of transfer factor?

Transfer factor seems to be well tolerated. But there is not enough research to know what the common side effects may be. Tell your health care provider if you have any side effects that bother you.

Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of transfer factor?

Based on limited research, serious side effects of transfer factor are described below, along with what to do if they happen. Other serious side effects are possible.

Severe Allergic Reactions. Because transfer factor products are made from animal tissues (such as cow colostrum or pig spleen), allergic reactions are possible and can be serious. Stop taking transfer factors and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use transfer factor?

Allergies to Ingredients. People who are allergic to any of the following should not take transfer factor.

  • Transfer factor
  • Dialyzable leukocyte extract (DLE)
  • Cow (bovine) milk or dairy products
  • Pig (porcine) products
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific transfer factor products they stock.

What should I know about transfer factor before using it?

Transfer factor is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep all supplements and medicines out of the reach of children.

The exact composition of transfer factor products is not fully known, and there is no standardized manufacturing process for these products. This means that different brands or batches may contain different amounts of active substances. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

Transfer factors can affect the immune system. People with autoimmune conditions (conditions where the immune system attacks the body's own tissues) should use caution and talk to a health care provider before using transfer factor.

The FDA has not tested transfer factor products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using transfer factor?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if this supplement is right for you.

In particular, make sure that you discuss any of the following.

Other Medicines and Supplements. Transfer factors may interact with other medicines and supplements. Before using transfer factor, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Autoimmune conditions (such as lupus, rheumatoid arthritis, or multiple sclerosis)
  • Immune system problems
  • Organ transplant
  • Cancer
  • Infection
  • Sensitivity to specific product source (such as cow milk, eggs, or pig-derived products)
  • Liver or kidney problems

Pregnancy. It is not known if or how transfer factors could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if transfer factor passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does transfer factor interact with foods or drinks?

No interactions between transfer factors and foods or drinks have been identified, though research is limited.

It is unknown if drinking alcohol will affect transfer factor.

Does transfer factor interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

Because transfer factor can affect the immune system, it may interact with medicines that suppress or change the way the immune system works, such as medicines used after organ transplants or medicines used to treat autoimmune conditions.

The interactions between transfer factors and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with transfer factors are limited. Always check with your health care provider before taking transfer factor with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much transfer factor?

If you or someone else has used too much transfer factor, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Transfer factor comes in a range of doses and forms, most commonly as capsules or tablets. Read the product label closely and speak to a health care provider about how to use transfer factor safely. Do not take double or extra doses, even if you miss a dose.