Is there a benefit to scratching that itch? Yes and no, says new study | Hacker News Reader

Is there a benefit to scratching that itch? Yes and no, says new study

newatlas.com

44 pointszfg40 comments

I have eczema, and I feel like most people who don’t have it cannot understand the experience of giving in to the urge to scratch affected skin after a period of trying to resist it. The best way I can describe it is an orgasm, the length and intensity of which you can directly control. It really is that intense. Why would we have evolved to have such an extreme pleasure response to something negative? And yet the effect of scratching on the skin seems very clearly negative. As a sufferer, it’s psychologically very difficult and confusing.

For persistent itches, a most effective remedy I've found is to pour hot water on it. Not burning - but as hot as you can possibly stand without burning. The hotter the better.

It is only briefly painful, but it kills itches completely. I don't know why it works, but it definitely does work.

Just be careful if you believe the itch is the result of something you might be allergic to (e.g., food, or bug bites).

I had several bites from fire ants and ran them under hot water from the bath, which seemed to trigger (or accelerate) a full-body reaction (anaphylaxis?) and a harrowing trip to the emergency room!

Hear is going to open the skin pores and relax veins/arteries, so it could be problematic for such things.

Ouch. Don't use heat to combat the symptoms of the bite of any venomous animal or any other one that secrets stuff into your body (mites, mosquitoes, etc).

It's hard to tell people to do things that reduce their blood flow, because it comes with complex side effects; but definitively not do anything that increases your blood flow. (As in, if you are feeling sick, do not eat peppers either.)

For mosquito bites, I thought hot water was recommended and effective?

https://pmc.ncbi.nlm.nih.gov/articles/PMC10309056/ supports this.

Because virtually nobody is allergic to mosquito bites. Accelerating the blood flow/metabolism of someone maybe at risk for anaphylaxis (bee allergy) is extremely dangerous.

It's effective, yes.

But when you have more than a few bites, you probably will not want to do that. Even more if you feel them a lot, and if you are not used to have lots of mosquito bites on you.

There are penlike devices that apply heat and remove the itch as well. propably safer and more accessible that hot water.

Afterbite. Its mostly acid and other caustic stuff to clean the area and kill off any nerve endings immediately inside the bite wound. It works. Just don't itch too much before applying. Afterbite on a scratched bite hurts like acid on a wound ... which it is.

https://afterbite.com/

For large swaths of dry skin, I've found that dragging a (retired) credit card across the skin works incredibly well.

It's rough enough to scratch the itch, but gentle enough to not break the skin.

I've done it with an active credit card and it does the trick, too.

Yeah but the fees are outrageous.

I bought a loofah pad and it works amazingly well. Never breaks the skin.

Yep, for mozzie bites there are pens that have a hot tip that you press on the itch. I think the heat breaks down the stuff (protein?) that is causing the itch.

> as hot as you can possibly stand without burning

Hm, this is the same way to treat stingray wounds. Something something bloodflow vasodialator?

My understanding about hot water is that it causes localized histamine release, which then depletes the available histamine to trigger the itch reflex.

Certainly works great for poison oak and eczema, regardless of the actual mechanism.

Many sea-animal toxins are protein based, and heat will denature the protein making it harmless. Similarly, acid (like vinegar) can help, e.g. for jellyfish stings.

(And if the toxin has penetrated your skin by e.g. the sharp tail of a stingray, heat will be better than vinegar since you can't get the vinegar "inside" your body... whereas jellyfish toxin tends to sit on the surface of your skin)

As others have said, it depends on the cause of the itch.

I have an alpha-galactose allergy. This is sort of a food allergy: beef and lamb, probably venison and to a lesser extent pork, trigger it. But unlike other food allergies, this doesn't hit me at the time, but maybe six or eight hours later. While I can get hives whenever I eat too much of that kind of meat (which of course I try to avoid), the best guarantee that it will happen after such a meal is heat on my skin. Initially, this happened several times when I stopped running after an hour or so, and my body was no longer cooled by the breeze and by breathing hard; but I've also gotten hives when taking a hot shower hours after eating beef, or sleeping under more blankets than I really need.

BTW, the alpha-gal allergy is transmitted by bites of the Lone Star Tick. You don't get hives from the bite, but it somehow makes you allergic to beef. And I'm not making this up--it is well documented: https://www.mayoclinic.org/diseases-conditions/alpha-gal-syn...; see also https://en.wikipedia.org/wiki/Exercise-induced_anaphylaxis on the link between exercise and hives.

Hmm but this was an allergen, where having more white blood cells at the site isn't beneficiary. If it was bacteria or a parasite, then the story might be very different.

TFA:

  "That being said, because mast cells are also involved in innate immunity, the researchers wondered if scratching's role in activating them conveys some kind of infection-fighting benefit.
  
  Sure enough, they found that scratching did in fact reduce the amount of Staphylococcus aureus on the skin. S. aureus is the most common bacteria involved in skin infections and is most famously responsible for staph infections.
  
  Still, in the research team's opinion, the reduction in this bacteria from scratching doesn't outweigh the way in which the behavior worsens the area around an itch."

Which doesn't address what the parent comment is about. They didn't infect them with parasites, or any number of other issues that cause an itching sensation.

It addressed most of the comment. Most directly, the "bacteria or..." part. And I'm sure the immune response to a parasite isn't exactly the same, but it's not hard to extrapolate that the same principle of increased immune activity being beneficial applies in that case as well.

> in the research team's opinion

This statement is carrying a lot of weight, and isn't properly justified.

The authors say the reason the skin gets so inflamed is the presence of all the immune cells. They then go on to say that the immune cells seem to kill potentially harmful bacteria in the area.

What is the reason they say that the body's response is problematic?

It sounds a bit like saying that the fact that our upper arms become sore after an vaccination (also immune-response related) outweighs the benefits that having vaccination has.

It's not that the body's response is problematic. It's that scratching is still problematic even if it does help some. The main issue with scratching is that it injures the surrounding skin including mostly healthy or completely healthy skin. This comes with a host of problems that are well established in plenty of other literature:

- Contaminating the site

- Spreading whatever is causing the initial wound

- Weakening the skin barrier and allowing whatever contaminant/infection to penetrate deeper/spread below the skin.

TLDR: They show a potential benefit of scratching (which may explain why it evolved in the first place) but suggest it doesn't outweigh all of the established harms.

Ages ago I started trying to scratch itches through some fabric, like a shirt sleeve or something, so I wouldn't damage the skin (keep the fabric stationary on the itchy skin and drag your hand across the fabric). For some reason it's almost as satisfying as scratching directly, so I wonder if it gets the benefit without the downside here.

I've found that gentle rubbing/massage has the same effect, although I need to remember it.

also scratching through clothes hasn't always stopped me from drawing blood.

This is what I recall being taught as a kid with bad allergies and various skin conditions. Rubbing can be helpful. If so, consider rinsing with water to make sure you don't have any residual thing there upsetting your skin.

Scratching through fabric is difficult because, if it does work, it could also trap the irritant in the fabric.

I just press my nail into it, to avoid scratching but to still cause the counter-itching effect.

This article was about itching due to bug bites or skin disease. In my case, my back sometimes develops several itchy spots as I undress for bed. I use a back scratcher, not too heavily, the itches seem satisfied, and don't return. There's no skin damage that I'm aware of. I find it hard to believe that this is somehow harmful.

Lab Mouse is officially the worst job in the world.

I always thought the dry skin causes the itch (when I don't see any bug bites). So scratching would relieve us from dry skin. But, I learned something today.

Yes, (very) dry skin can also itch. In that case I would suggest moisturizing cream, scratching definitely won't make it go away...

We already knew that scratching causes an inflammatory response. Where the specific mechanisms involved that the study found previously unknown?

(editted to reword my question)

I always figured it was just to increase blood flow. That's the reason that hot water also satisfies the itch, it increases blood flow as well.

... but it hurts so good!

(in mice)

tl;dr Scratching an itchy spot boosts the local inflammation and immune response.

I know people hate the "just so" stories, but from an evolutionary perspective it makes sense. You get a parasite, it itches, you scratch it, which removes the parasite and kicks up the local immune response.

> which removes the parasite

This is probably one of the big evolutionary factors they didn't mention. Scratching at mosquito bites after the mosquito is already gone might just be an unfortunate side effect.

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