Acrylamide in Migraine Ice Caps: What Two New Studies Found

Why This Matters for People With Migraine

Gel ice caps are one of the most popular non-drug tools for a migraine attack. You freeze the cap, pull it over your head and eyes, and the cold and darkness help some people get through the worst hours. Many people with migraine wear one several times a week, sometimes for an hour or more at a time, directly against the forehead, temples, and scalp.

In August and October 2026, two veterinary papers reported that the gel inside several of these caps contained very high levels of acrylamide, a chemical that damages nerves. Both papers came from animal poison control centers, because dogs that chewed the caps got seriously ill and many of them died. Nobody has reported a human poisoning from wearing a cap. But the findings raise a question that people who wear these caps against their skin deserve an answer to, and as far as we can find, the brands haven't given one.

What Acrylamide Is and Why It's in the Gel

Most reusable cold caps are filled with a hydrogel, a soft, water-holding gel that stays flexible when frozen. A common recipe is polyacrylamide, which manufacturers make by linking small acrylamide molecules into long chains. The finished polymer itself is considered nontoxic. The problem is the leftover acrylamide that never got linked into the chain, called residual monomer.

Acrylamide on its own is a well-known nerve toxin. In people, too much exposure causes damage to the peripheral nerves, which shows up as numbness and tingling in the hands and feet, along with effects on the brain. The International Agency for Research on Cancer classifies it as probably carcinogenic to humans (Group 2A), and the US National Institute for Occupational Safety and Health gives it a skin notation for systemic toxicity, meaning it can be absorbed through the skin in amounts that affect the rest of the body.

A well-made polyacrylamide gel should contain very little leftover acrylamide. The cosmetics safety review that set the 5 ppm limit for skin products reported that commercial polyacrylamide usually contains somewhere between less than 1 and 600 ppm of residual monomer, and the European Union limits leave-on cosmetics to 0.1 ppm. Medical device grade hydrogel is held to 1.5 ppm or less.

Study 1: 45 Dogs Reported to ASPCA Poison Control

The first paper, published on October 2, 2026 in the Journal of the American Veterinary Medical Association, came from ASPCA Poison Control, working with the Product Injury Coalition, polymer scientists at Cambridge Polymer Group, and an emergency veterinarian. It is a case series, meaning the authors went back through their poison control records from January 2024 to June 2026 and described every dog with strong evidence of exposure to a hydrogel migraine cap, eye mask, or wrap.

They found 45 dogs. Vomiting was the most common first sign, followed by a fast heart rate, seizures, unsteady walking, and tremors. Some dogs became anxious, agitated, or aggressive, and one appeared to hallucinate. Signs generally started within 12 hours. Of the 21 dogs whose outcome was known, 14 died or were euthanized, usually within a day.

The researchers then tested gel from two of the cases and a migraine cap they bought from the brand involved in 7 of the exposures. All three contained between 12,900 and 51,800 ppm of acrylamide. That is 21 to 86 times higher than the upper end of what is reported across industries, and 8,600 to 34,500 times higher than the specification for medical device grade polyacrylamide hydrogel. The paper didn't name the brands.

In the press release that accompanied the paper, the lead author said ASPCA Poison Control now receives reports like these every week and that the problem has been seen across many brands. The release also noted that these products are often labeled "nontoxic" or "medical grade," and that acrylamide can be absorbed through the skin as well as by mouth.

Study 2: Three Dogs and Two Named Products

A second case series, published in August 2026 by toxicologists at Pet Poison Helpline and the University of California, Davis, described three dogs that ate parts of hydrogel headache products. All three died or were euthanized after seizures and a rapid decline.

This paper named the products it tested. An unused Miracle Headache Relief compression wrap contained 3,600 ppm of acrylamide. The TheraICE Headache Hat contained 13,000 ppm, both straight out of the package and after being used as directed, and gel recovered from one of the dogs contained 9,300 ppm. The authors noted that acrylamide was listed in the TheraICE product's publicly available ingredient information, and that judging these gels as low risk from their labeled ingredients alone could underestimate the danger.

The authors called for standard limits on residual acrylamide in consumer hydrogels, better labeling, and safety data sheets that are easy to find.

How the Measured Levels Compare

Measured acrylamide in migraine cap gels next to the limits and typical levels for other polyacrylamide products.

Can It Reach Your Body Through the Cap and Your Skin?

The dogs ate the gel, and swallowing is a much more direct route than skin contact. People don't eat their migraine caps, so the question for us is whether acrylamide can get from the gel, through the cap, and through the skin in meaningful amounts. Here is what the evidence says about each step.

Step 1: The fabric between you and the gel is thin and porous

Migraine caps are made to stretch and hug the head, so the outer layer is a thin knit fabric. The TheraICE Amazon listing gives the fabric as 82% nylon and 18% spandex, and lists the gel ingredients as water, glycerin, acrylamide, methylene bisacrylamide, and acrylic acid. A stretch knit like this lets air and liquid pass through, which is part of what makes it comfortable. It isn't designed to be a chemical barrier.

TheraICE's care instructions describe the gel as sitting inside an inner lining beneath that fabric. The company's own care instructions tell users to check that lining for tears before every use, to apply the cap to dry skin only, not to use it when wet, and to wash with soap and water if the gel touches skin or eyes. Those warnings tell you two things. The lining can tear with normal use, and once it does, nothing but a thin knit separates the gel from your forehead. The instructions also tell you to heat the cap in the microwave for warm therapy, and repeated freezing, heating, and stretching are the kinds of stress that wear out a thin lining.

Step 2: Acrylamide gets through human skin

Acrylamide is a very small molecule that dissolves easily in water, which is what a hydrogel mostly is. In a lab study by FDA scientists, acrylamide applied to human skin in a cosmetic cream penetrated quickly, peaking at 6 hours, and about half of the applied amount had penetrated the skin by 24 hours. When it was applied in a 2% polyacrylamide gel cream, about 39% penetrated. The cosmetics safety panel reached the same conclusion, that acrylamide residues do penetrate the skin, and that is the reason it capped cosmetic levels at 5 ppm.

In mice, acrylamide put on the skin was absorbed, spread through the body, and caused genetic damage in sperm-producing cells. In people, a Swedish study of 210 tunnel workers exposed to an acrylamide grouting agent for about two months found a clear link between the amount absorbed and nerve symptoms. Among workers with the highest blood markers, 39% had tingling or numbness in their hands or feet. Most recovered within 18 months after the exposure stopped.

Step 3: The head absorbs more than most skin

Skin on different parts of the body absorbs chemicals at different rates. Classic studies in human volunteers found that the scalp, forehead, and angle of the jaw absorbed about four times as much as the forearm, likely because these areas have a high density of hair follicles. A migraine cap covers the scalp, forehead, and temples, which are among the most absorbent skin on the body.

Put together, the parts of this chain are each supported by evidence. Some caps contain thousands of ppm of acrylamide, the fabric over the gel isn't a barrier, linings can tear, acrylamide passes through human skin and enters the body, and the head is one of the more absorbent areas. What no one has done is measure how much acrylamide reaches a person who wears one of these caps. Until someone does, the risk to people can't be ruled in or ruled out.

What the Brands Say, and What They Don't

On October 31, 2026, we checked the Amazon listings for the five brands at the top of an Amazon search for "migraine relief cap": TheraICE (Headache Hat and Headache Hat PRO), MyHalos, ONLYCARE, Beyio, and Qnoon. We also checked the TheraICE website. We searched each listing and the TheraICE website for any mention of acrylamide testing, residual monomer limits, third-party lab results, or a safety data sheet.

None of them mentioned testing for residual acrylamide. Instead, the listings lean on reassuring but undefined terms. TheraICE describes its gel as "medical-grade" on its website and "expert-grade" on its product page. MyHalos also says "medical-grade gel." ONLYCARE calls its gel "safe" and "advanced." Beyio says "high-quality gel." "Medical grade" has no standard definition for consumer cold packs, and as the JAVMA authors pointed out, "nontoxic" isn't a regulated term either.

Only one brand listed what its gel is made of. That makes it impossible for a buyer to know whether a cap is polyacrylamide-based in the first place, let alone how much leftover acrylamide it contains. Many cold packs use other gels, and listing no ingredients doesn't mean a product contains acrylamide. It means you can't tell.

Reusable hot and cold packs fall into the lowest-risk class of medical devices in the US and don't need FDA review before they're sold. We couldn't find any US limit on residual acrylamide in consumer cold packs or migraine caps, which matches what both sets of authors reported and why they called for one.

What These Studies Can and Can't Tell Us

• Both studies are about dogs that ate gel. Their findings on illness and death don't transfer directly to people wearing caps. Swallowing gel delivers far more acrylamide, far faster, than skin contact. This is a question of generalizability, and it cuts in favor of caution, not alarm.
• Few products were tested. The two papers measured acrylamide in six gel samples from a small number of brands. We don't know how common high levels are across the market, or whether levels vary from batch to batch.
• No one has measured human exposure from wearing a cap. There are no studies measuring acrylamide on the skin under a cap, in the blood of regular users, or in gel that migrates through intact linings.
• No human cases have been reported. That's reassuring, but also expected, because low-level exposure would cause vague symptoms like tingling or fatigue that nobody would think to link to a migraine cap.
• The case series design can't prove cause on its own. The dogs had no blood acrylamide measurements and the amount eaten was unknown. The pattern of symptoms matched known acrylamide poisoning, and the gel levels were very high, which makes acrylamide the most likely explanation.

If You Use a Migraine Ice Cap

Cold therapy itself isn't the problem. It's a low-risk, drug-free option, and it can help people who are trying to limit how often they take acute medication. If you're not sure whether you're in that range, our medication overuse headache checker can help. The concern is the gel some caps are made with, and there are practical steps you can take while better testing is missing.

If you share your home with a dog or cat, the pet risk is the clearest finding in these studies. Many people with migraine also have pets, and our article on what a 3,017-person study found about pets and migraine covers how pets fit into life with migraine. Store caps in a closed drawer or high cabinet, not on a nightstand or couch.

If you're looking for other non-drug options for a migraine attack, our review of whether neuromodulation devices for migraine work covers the devices with trial evidence behind them. Bring up any treatment questions at your next visit, and our free migraine appointment summary sheet can help you keep track of what you want to ask.

We'll update this article if brands publish test results or if new studies look at human exposure. To follow new migraine studies as they come out, see our daily migraine research news.