#if it's actually not-technically-autoimmune (mcas)

[kirby-the-gorb]

[cesium-sheep]

also, btw, while sm isn't technically cancer (just like mcas isn't technically autoimmune the bastard) it does have its own page on cancer.net, so.

[gncrevan]

Your Guide to the Most Common Antihistamines

H1-Antihistamines

These are what we commonly think of as antihistamines, also known as anti-allergens.

First Generation H1-antagonists are precursors to antipsychotics. They often have a psychotropic effect and tend to calm you down in low doses. Work well as antiemetics against nausea and vomiting. High doses may in some cases cause hallucinations. Often very sedating.

Diphenhydramine aka Benadryl: for some reason really popular in the U.S.? Other countries mainly use it to aid sleep, or to treat an anaphylactic shock. Known to be hallucinogenic in high doses or when mixed with alcohol. IT IS NOT A COLD MEDICINE. ANTIHISTAMINES DON'T HELP AGAINST INFECTIONS.

Dimenhydrinat aka Draminate, Dramamime: a combination of Benadryl and Theophyllin, which is a bronchodilator. Used to treat nausea, vomiting and motion sickness. Due to its highly sedating effect, also used to aid sleep. Like Benadryl, it can cause hallucinations in high doses.

Dimetindene aka Fenistil: very popular in topical cream to treat sunburn or insect bites. In cases where a person doesn't react well to second generation meds, this is usually the go-to alternative, as it is not particularly psychoactive. However, it tends to be very sedating. Most commonly used in relatively high doses either orally or IV to treat anaphylaxis. Can interact badly with tri-cyclical antidepressants!

Second Generation H1-antagonists are safer and cannot be overdosed easily as they don't have extreme side effects. They are less sedating and not psychotropic. If you don't happen to react badly to these, they're the best option available to treat allergies, histamine intolerance or mast cell disease.

Cetirizine aka Zyrtec: your average over-the-counter allergy med. Slightly sedating, but highly effective. Treats hayfever, urticaria, dermatitis etc. Generally advised to be taken before bedtime.

Loratadine aka Claritin: also generally over the counter. Said to not be sedating at all/have no effects on the central nervous system. Treats allergies, eczema etc.

Fexofenadine aka Allegra: sometimes also called a third generation med cause it's technically a derivate of Terfenadin. The latter had a risk of cardiovascular problems that is much reduced in Fexo. It's also not particularly sedating in my experience. I take copious amounts of this as it's a staple to treat MCAS/mastocytosis. It's not available over the counter.

Ketotifen aka Zaditor: also acts as a mast cell stabilizer in addition to being an antihistamine. Treats mast cell disorders, asthma attacks, anaphylaxis and various allergies.

H2-Antihistamines

These decrease stomach acid production (kinda like PPI) and are commonly used to treat reflux, gastritis and other acid-related stomach issues. Since PPI like omeprazole have been found more effective, H2-antagonists have generally fallen out of use, except in therapy for mast cell diseases and in cases where a PPI is not tolerated.

Ranitidine aka Zantac: appears to be the most popular one. Can sometimes cause dizziness, sleepiness, tachycardia and malabsorption.

Cimetidine aka Tagamet: no observable side effects or possibility to overdose. Can interact negatively with tri-cyclical antidepressants, blood pressure medicine, opioids, and a lot of other drugs.

H3-Antihistamines

Kinda rare, sometimes used to treat vertigo and Morbus menière but the effectiveness seems to be controversial.

H4-Antihistamines

As far as I can tell, these are not yet in use. They appear to have anti-inflammatory properties that are being examined.

General Note

All antihistamines can negatively affect your cardiovascular system, cause headaches, and dryness of the mouth. They are also completely broken down via your liver, so as with any medication, if you take it over an extended amount of time, get regular blood checks. That said, especially the newer generations are relatively safe and have few to no side effects. Every medication comes with a certain risk, but antihistamines are in general a lot less risky than for example pain meds, asthma meds, blood pressure meds etc.

However, antihistamines can only treat things that are allergic or autoimmune! They are not beneficial against infections, in fact they actually suppress your immune system. This might be helpful in some cases, for example to not make you throw up, as this is controlled by histamine, but it can only alleviate some symptoms in those cases. If you have allergic inflammations, it can help, especially if used directly on your skin, in your nose or eye, and it can counteract allergic reactions in your body, but it cannot fight bacteria or a virus. Please don't treat your cold with benadryl! Also please don't treat your allergies with benadryl if you have other options, second gen meds are much safer!