So my conclusions from the growing lists of allergies I have accumulated over the years, foods you can try and see how you react, it will be almost instantly or within 24 to 48 hrs. But a supplement has minimal quantities that it could become a cumulative effect and only react later as time goes by. I have allergies to iodine and used to eat some sea food but eventually when I tried Octopus at a wedding and my tongue swelled up right away after I swallowed the first bite, but at the time I did not know about iodine allergies and certain sea food cross allergies. I took Benadryl around the clock every 4 hrs and it was OK, but I now stay away from all shell fish or animals such as octopus, squid who skirt ink so to speak. So it is up to you if you wish to try it out once you get all the information from your pharmacist, or look up the few links I have left you in these reply.

Thanks for this question, as you brought up an interesting subject here. I have ragweed allergies also. Milk thistle can cause an allergic reaction, including a severe, potentially life-threatening allergic reaction (anaphylaxis). An allergic reaction is more common in people who are allergic to other plants in the Asteraceae family, such as ragweed, daisies, marigolds and chrysanthemums. https://www.mayoclinic.org/drugs-supplements-mi....

https://allergyasthmanetwork.org/allergies/poll...

What foods are related to ragweed? You may need to avoid certain fruits and vegetables if you re allergic to ragweed and develop symptoms from eating these foods. This happens because foods botanically related to ragweed can trigger what is known as oral allergy syndrome (OAS). Foods in the ragweed family include: artichoke, banana, chamomile, cucumber, echinacea, mango, melon (watermelon, cantaloupe, honeydew),
sunflower seed, zucchini. Here is a link to what they spoke of on the previous link above about the oral allergy syndrome (OAS). There is a bigger list of certain foods people may have allergic reactions to depending on your allergies : https://allergyasthmanetwork.org/health-a-z/ora...

It does not automatically mean that if you are allergic to ragweed that you will develop an allergy to other foods, but there is a risk of Cross allergies. In my case I cannot eat anything in the melon group, I have tried a few times in the past when I did not know about the link. When I try and eat watermelon or cantaloupe as soon a it hits my tongue I get an aversion to it and my tongue gets prickly feeling kind of like a numbness, it is hard to explain but it actually tastes so awful to me, a work colleague doctor told me about the link of certain foods and ragweed. But I am able to eat cucumbers, bananas, tomatoes and many other foods mentioned on a few sites.

But other then food allergies that come along with being allergic to ragweed is a latex allergy, when I became allergic to latex gloves (I worked as a nurse) I got exposed a lot to it and eventually developed a skin rash on my hands, then it progressed to having asthma attacks just from the smell of them if a colleague was wearing them next to me, (I graduated in 1988 and allergy started in 2000. So once staff health realized a few of us health care workers developed allergies to latex, they switched to Nitrile gloves even for our non sterile ones in our hospital, as many of us reacted badly, that is when they tested me and a few others for various allergies and found most of us also had ragweed allergies. https://www.jacionline.org/article/S0091-6749(0.... CONCLUSIONS: Latex, goldenrod, and ragweed may share cross-reactive antigens. However, the presence of goldenrod or ragweed sensitivity does not necessarily cross-sensitize to latex and there are unique latex antigens that do not cross-react with goldenrod or ragweed.

So the warning on the bottle of your Milk thistle you may want to discuss your pharmacist , they know of every reactions possible or have access to database for them when they need to access it. The pharmacist can help you decide whether you should continue with taking it, as they have your other prescriptions in your file and can also see if some interactions are present with other medications you may be on

Thank you for your informative response