How does IcyHot work?


Just put some on my knee and i’m a little amazed.

In: Biology

Depends on the active ingredient but if it’s the lidocaine product it decreases the permeability of sodium ions in the membrane of the nerves that conduct pain. In doing so it prevents the conduction of the signals of pain.

Ions are important in the conduction of electrical impulses in the body and sodium is one of the most common elements used. In the heart you will also see calcium ions used. Whenever you block these ions you prevent the body from sending these electrical signals.

Probably capcasin (same stuff in chilli that makes it sting). Basically it overstimulates sensory neurons in the area you apply it.


When your brain detects a bunch of signal firing constantly as noise, it just ends up blocking it eventually.

These pain relievers don’t really address pain. They just make a lot noise so your brain puts on some earplugs to ignore those particular signals.

IcyHot’s main active ingredient is Menthol. It’s a commonly used analgesic. That and salicylic acid.

That’s it. Found it numerous pain relievers.

The original IcyHot contains menthol, which will affect the nerves that bring pain signals to the brain. Essentially, the menthol will stimulate those nerves to “oversend” signals to the point that the nerves get “fatigued.” They have sent so many signals so quickly that they exhausted most of the sodium that can fuel the nerve impulses. Capsaicin will do the same thing, and that may be the “hot” part of the original formula. (There are so many products being made by them, it’s difficult to remember what the original product contained.) The lidocaine version has already been explained in detail. Some of them contain methyl salicylate, which is in the salicylate class and is an anti-inflammatory drug, like aspirin. The explanation for the anti-inflammatory effect would be above ELI-5 level but let me know if you’d like a quick breakdown. It doesn’t really work that great because it doesn’t get absorbed transdermally very well but that doesn’t stop everyone from marketing the stuff. I think the best indication for those is arthritis in the hands because the skin is so thin there and the absorption doesn’t need to be so deep to help. (Same thing with Voltaren gel.)

Edit: Source: Pharmacist

Edit 2: For those that asked about how NSAID anti-inflammatoy drugs work:

This involves a chain of events that cause inflammation, pain and swelling after an injury. Once an injury occurs, there are chemical and/or physical occurrences that signal a pathway to activate. A pathway is just a series of events that happen one after another that leads to an end result. Let’s say you fall and hit your elbow on the ground but don’t break any bones. That force causes some minor structural damage that signals an inflammatory response. Arachidonic acid is converted by enzymes, cyclooxygenase (COX) 1&2, to prostaglandin G, which is then converted by another enzyme to prostaglandin H, further converted by another enzyme to specialized prostaglandins, prostacyclins and thromboxane. These compounds cause the local blood vessels to open up to bring fluid (swelling), platelets (stopping bleeding) and other components that promote healing. Now, don’t get overwhelmed by the names of these things, as that’s not necessarily important. I included them so you get an idea of how this pathway works. Notice I only included the name of one enzyme step and that’s because that is where NSAIDs work. They stop COX 1&2 (yup, it’s a COX-blocker) from working so that most arachidonic acid is never converted to prostaglandins G/H, which (mostly) stops the pathway there. (It’s not 100% and it’s temporary, which is why you’ll still get some pain, swelling and inflammation and will have to take further doses.) As a side note, I also mentioned platelets for a reason. Many people know aspirin is a blood thinner but fewer know the other NSAIDs are, as well, but to a lesser degree. If you stop this pathway, platelet production is also slowed which means your blood will not clot as quickly as before. It’s possible you could take ibuprofen or naproxen for the pain and swelling and end up with a slightly worse bruise but feel better. It’s also why you shouldn’t take these 5-7 days before a surgery or giving blood.




The smell just distracts you enough that you forget about your pain because you’re concentrating on not throwing up. /s

I honestly have no idea but this stuff makes me so sick to my stomach and gives me headaches

I had a doctor tell me it’s kinda like if you come in with a toothache. And then the doctor slaps you and asks if you still feel the toothache. That’s what the “hot” part of icy hot does.

I don’t know much about it but hopefully that’s ELI5.

A lot of people are answering chemically but I’ll try and answer physiologically.

The cooling and heating acts to “compress” and then “release” on the afflicted area. This wave of compression and release is like a massage that will get blood flowing through the area. The intention is to 1) use this blood flow to flush out localized lactic acid (Or lactose dehydrogenase) and 2) to encourage aerobic metabolism by bringing more fresh blood with oxygen to the site.