eli5: Why does donating blood risk triggering an existing autoimmune disorder?

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This is not a false premise, I am not eligible to donate blood for this reason.

In: 7

Off the top of my head I can’t think of any reason why it would be dangerous for *you*, but if you have an autoimmune disease that involves, say, self-reactive T cells or antibodies, then that poses a danger to the recipient.

E: MSc in immunology

It’s not that it triggers a disorder in you, the donor. Historically, the were concerns that it could trigger a disorder in the recipient because of antibodies and immune cells in the blood. Also, people with autoimmune disorders take strong meds to suppress the immune system which could also affect the recipient.

The only reason that it might be a risk for the donor is stress. A lot of autoimmune disorders flair up due to stress (phisycal or mental). With donating blood you are causing stress to the body (now you have to produce more than usual blood cells) which can sometimes trigger an immune response (headaches, fever,). If the situation allows it, and you have autoimune disorders in the family, generally are tired, over worked, stressed out mentally it can be a trigger. Even if you have an autoimmune disorder that is under control its not advisable to donate blood for your sake (may cause flair up, stop the remission) and for the recipients sake.

While I’m resident physician specializing in emergency medicine and not rheumatology, to my knowledge there’s several possible reasons.

There is a [list of medications](https://www.redcrossblood.org/donate-blood/manage-my-donations/rapidpass/medication-deferral-list.html) that include some treatments for auto-immune diseases, and I know of several off the top of my head not listed (Methotrexate, Hydroxychloroquine) that are commonly used in auto-immune diseases like RA/Lupus, that are toxic and not appropriate for blood transfusion. This could be a reason to exclude you.

Often people with auto-immune diseases are prone to infection, both because of their condition and the medicines they take for it. So any needle puncture is a chance for infection. When doing preventative medicine labwork or IV access during hospitalization, the risk and benefit is weighed and the benefit of having IV access (particularly in the hospital) usually outweighs the risk. But in blood donation, a pint of blood is not worth risking sepsis.

People with auto-immune diseases are also often anemic, which excludes from blood donation. My experience has been that this is tested on every donor, but perhaps some donation sites see it as a cost-saving measure. By excluding people with chronic anemia, they save the cost of testing. This is hypothetical, I don’t know if this is true.

As far as I’m aware, receiving blood from someone with an auto-immune disease such as rheumatoid arthritis, lupus, etc does not pose any greater risk to the recipient so long as they’re not on potentially harmful disease-modifying therapies. I could maybe see the hypothetical, but I’d be far more interested in reading applicable literature.

[Here’s an appropriate NIH article](https://www.ncbi.nlm.nih.gov/books/NBK138205/) worth looking over if you’re interested. It’s not ELI5 level, but it’s also not inaccessible.