Antihistamines and your immune system. - British Lung Foun...

British Lung Foundation

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Antihistamines and your immune system.


I will emphasise that if you have been prescribed antihistamines by your GP or consultant that you should ask for further advice, not to just stop taking them. I am just making this post for those that self medicate for pollen allergies and it will depend just on how bad pollen affects them. Obviously we need our immune systems working as well as can be. Worth thinking about.


How antihistamines work

"Antihistamines work by blocking the effects of a chemical called histamine in your body. Histamine is made by your immune system to protect you from infections."

15 Replies

Interesting. I have prescribed antihistamines but never thought about how they work or what other effects they have on the body 🤔

As I stated, please consult with you GP, over the phone of course, before stopping to use them.

No worries 2greys, your post just made me think. Sometimes I feel like it doesn't occur to me to think about things. It's good to learn and be enlightened 👍


Thanks 2greys - useful guidance, as always. One thing that occurs to me is that, although antihistamines are described as "blocking" the immune response, I suspect the effect is incomplete. They might only block the excessive immune response from an allergy, and possibly leave sufficient response to real pathogens. Do you know of any research which clarifies this?

I will trawl for more info into this, I would suspect that there may be a knock on effect to the rest of the immune system though, more later.

Hi Trevor, whilst I will still look deeper, for the viral implications. This study does imply a reduced immune response to bacterial infection. This is important because I think that it is not Covid-19, the virus, that gives rise to mortality, it is the additional, secondary bacterial infections that cause the mortality ie. Pneumonia.

Although with the link below the research was done with mice, it is enough for me to stop taking Antihistamines as a precaution. I will put up with any sneezing, which will be less by staying indoors anyway.

Quote/"Conclusion: Our findings indicate that sedating first-generation H1R antihistamines and H2R blockers might impair innate immune responses to bacteria and that these drugs should be used with caution in patients with severe bacterial infections."

After looking for hours last night, I have been unable to find reference to any impact on viral immunity at all, just towards bacterial ummunity.

antihistamine has dose-response relation meaning that it does not know what is excessive. most of the asthma (ex prednisone) drugs are immune modulators. hardly any side effect studies. The other immunosuppressor drugs for RA and Osteoporosis have side effects such as reactivation of bacterial and viral infection. COVID-19 really put a lot of drugs under scrutiny.

Izb1 in reply to Maverick2

Thanks for posting this Maverick2, I did wonder about the methotrexate I take for RA as this makes your immune system inactive. I sometimes take antihistamine for bronchiectasis as the mucus makes me cough constantly x

Maverick2 in reply to Izb1

Methotrexate used for RA is relatively low immunosuppressive compared to TNF-alpha inhibitor and IL-6 inhibitor. that's the reason they are more responsive to RA. people on methotrexate have a mild increase in the infectious risk which can be balanced by taking Vitamin C and D.

Stay safe, we can get through this.

Izb1 in reply to Maverick2

I do take vit d but may add the vit c to this now, thank you. Yes lets stay safe and get through this x

Thank for this 2g, didnt realise they affected your immune system,a lthough being on methotrexate I wonder if I should worry about this x

2greys in reply to Izb1

Perhaps ask the question on that site I posted earlier, click on the box at the top right that says "Ask a scientist your question" I think that you get answer via your email. I am waiting for an answer myself, which I will report here later, when I get a reply.

You could phone your consultant/GP of course but I should imagine they will be very busy.

2greys in reply to Izb1

An answer here:


Izb1 in reply to 2greys

Thank you .

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