WASHINGTON (AP) — You’ve likely heard it since childhood: Don’t scratch that bug bite or rash, you’ll make it worse. But why would something that feels so good be bad?

A lot of things can cause itchiness, sometimes serious diseases. Whatever the cause, doctors have long warned that scratching too much can damage the skin. Now researchers better understand why even a mildly annoying itch could put you on an itch-and-scratch cycle if you give in.

How did they find out? In part by putting tiny “cones of shame” onto mice to uncover what happens on a cellular level when an itch gets scratched — or left alone.

They also gained insight into why a good scratch at least at first brings a sigh of relief. After all, not just people and other mammals scratch, even fish do. The commonality suggests there must be some evolutionary reason and the mouse experiment hints at a little germ protection — but still not a reason to scratch.

Expect a more swollen, itchier spot if you can’t ignore that bug bite

Dr. Daniel Kaplan, a University of Pittsburgh dermatologist whose lab studies immune reactions in skin, was exploring a run-of-the-mill type of itch called allergic contact dermatitis, caused by irritants such as poison ivy or nickel in jewelry.

Kaplan’s research team put a rash-inducing irritant on the ears of mice. Normal mice scratched and inflammatory immune cells rushed to the site, increasing swelling. The rash was much milder in mice bred with defective itch-sensing nerve cells. But was the difference really the scratching?

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Normal mice put into collars like those veterinary “cones of shame” so they itched but couldn’t scratch gave the answer: They, too, had much less swelling and fewer inflammatory cells.

Kaplan said that evidence matches people’s everyday experiences that scratching really can make things worse.

Ignore a mosquito bite and the itch is “gone in five or 10 minutes for most people,” he said. “But if you start scratching it, it’s your friend for a week,” getting itchier and more inflamed.

The immune system’s first responders can help — and hurt

To understand what was happening in the skin, Kaplan’s team took a deeper look at mast cells, among the immune system’s first responders. When called into action, they release compounds that can help fight germs or toxins — or, through a compound called histamine, trigger itchy allergic reactions.

Scientists have long known that allergens can activate mast cells. But other signals can summon mast cells, too, including pain. And when we scratch, “we tend to scratch until it starts to hurt,” Kaplan noted.

Pain-sensing nerve cells release a chemical messenger called substance P. In findings published last year, Kaplan’s team reported that substance P can activate mast cells through a different molecular pathway than allergens do — a double whammy that explains why scratching further inflames itchy rashes or bites.

Then why does a little scratching feel good?

If we experience pain like touching a hot stove, we’ll learn not to do that again. Yet relief from a good scratch, in evolutionary terms, is positive feedback. Why?

One long-held theory is that it may help creatures slough off parasites like fleas or mites. But Kaplan also was intrigued by other labs’ findings that mast cells could fend off a common type of skin bacteria called Staphylococcus aureus. So his team infected mice and then repeated the cone-of-shame itch experiment. Sure enough, those that scratched had lower levels of that germ on their ears, maybe because of the extra inflammation or some other mast cell-related compound.

But that’s not enough of an upside to change the health advice.

“Ultimately, scratching is deleterious,” Kaplan stressed. “You should avoid scratching,” he said, although acknowledging that it’s “easier said than done.”

Here’s how to handle a minor itch

What fights an itch depends on its cause and there’s a need for better treatments. For now, antihistamines and certain other drugs for hives can tamp down some itchiness triggered by mast cells. Drug companies are experimenting with other approaches called MRGPRX2 blockers that target the pathway Kaplan’s team linked to scratching. Kaplan hopes better understanding of that pathway eventually could help skin diseases such as chronic eczema.

For the summer itchiness of bug bites, poison ivy and other types of contact dermatitis, dermatologists recommend anti-itch balms such as hydrocortisone cream, calamine lotion or oatmeal baths.

Another trick from Kaplan: Menthol-containing creams can temporarily fool the skin into sensing cold instead of itch, just long enough that “if you don’t scratch, then you break that itch-scratch cycle,” he said. “It’s like a cheat code.”

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.

A recent report says one in 10 patients — equalling around 180,000 people — who were admitted to an emergency department in Canada spent more than 48 hours waiting for an inpatient bed in 2024-25.

In addition, about 1.5 million people spent more than 14 hours in emergency rooms during the same time span, a 28-per cent increase from 2018–2019.

The data released on Thursday by the Canadian Institute for Health Information highlighted that many emergency departments across Canada “are facing challenges with overcrowding, staffing shortages, and limited bed and stretcher capacity that have not kept pace with growing demand.”

The report says older adults and people with chronic conditions such as diabetes or high blood pressure are often in the emergency department the longest.

“Longer waits for physician assessment are associated with potential risks, including worsening clinical condition, reduced timeliness of care and a greater likelihood of adverse events,” the report reads.

There were 16.1 million visits to emergency departments across Canada in 2024-25, according to CIHI. Twelve per cent of those visits resulted in hospital admission.

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Cheryl Chui, director of health system analytics at CIHI, said that longer wait times “are really due to factors that are originating outside of emergency departments.”

“We’re seeing patients with more complex needs arriving in the emergency department as well as where we are seeing challenges moving patients through hospitals and into the next level of care when they’re ready to be discharged,” she said.

“So together, these pressures are contributing to longer wait times in the emergency departments, which means that improving emergency department wait times will involve looking at the entire health system.”

The report states that only age was associated with a longer wait time for a bed, as admission rates “increased with age, and older patients tended to wait longer.”

In addition, patients who could be discharged to long-term care homes, home care or rehab centres were found to be waiting an average of 24 days in hospital inpatient units.

“This likely reflects both bed availability and bed type. Younger patients are more often placed in the next available bed, while older patients with comorbidities or isolation requirements must wait for an appropriate bed, such as an isolation bed or a bed on a specialized unit.”

This is a sector of the health-care system that Dr. Michael Howlett, physician and former president of the Canadian Association of Emergency Physicians, believes needs fixing.

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“Our population demographics are increasing in age. Our population, therefore, is aging. We’re seeing many more people with multiple health conditions, significant complicated health problems, and they take a lot more time, a lot of work, a lot of hospital care, and then they take that much more care when we try to get them back into the community,” he said.

“There needs to be much more emphasis on how we as a society are going to take care of our elderly frail.”

In addition, the report cites “ongoing staffing shortages” that have led to temporary closures of some emergency department sites, with patients in rural and remote areas in particular being affected. One in four hospitalizations among people living in rural/remote areas were found to have “a high or very high travel burden — a burden which increases with the level of care specialization.”

This is an area that Howlett does not see improving quickly.

“The number of positions available for specialist trained emergency positions is not increasing. So, some provinces have very few [positions]. Human resources then become an issue,” he said.

Chui also added that “tackling emergency department wait times is really a health system issue that extends beyond the emergency department and the hospital.”

“We see the symptoms of the pressures across the health system manifesting in longer emergency department wait times. But our data suggests that improvements will require system-wide coordinated action across multiple sectors, including primary care, hospital, home, and community care and long-term care.”

Health Canada has approved weight-loss drug Zepbound for treating obstructive sleep apnea in adults with obesity.

The department confirmed that the authorization granted on June 11 makes Zepbound the only GLP-1 drug in Canada approved for the sleep disorder that causes people to stop breathing temporarily because their upper airway is blocked.

That blockage can happen when throat muscles relax or when there is too much fatty tissue around the upper airway.

Sleep apnea causes daytime sleepiness and other potential risks including high blood pressure, heart attacks and strokes, said Dr. Mandeep Singh, a clinician investigator in sleep science at University Health Network in Toronto.

It is often associated with obesity and can be improved with weight loss, he said.

The active ingredient in Zepbound is tirzepatide, which acts on both GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide) hormone receptors to reduce appetite, leading to weight loss.

Eli Lilly’s tirzepatide medications, including Zepbound and diabetes drug Mounjaro, are competitors to Novo Nordisk’s semaglutide drugs Ozempic and Wegovy.

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Health Canada spokesperson Marie-Pier Burelle said tirzepatide should be injected once a week and used alongside a reduced calorie diet and increased physical activity in adults with obesity measured by a body-mass index (BMI) of 30kg/m2 or higher.

The drug is “not an immediate replacement” for continuous positive airway pressure — or CPAP — that is a first-line therapy for moderate to severe sleep apnea, Burelle said.

“Patients taking Zepbound should not stop using their CPAP machine without a doctor’s guidance,” she said.

Health Canada’s approval follows Phase 3 clinical trials with patients who had both obesity and sleep apnea.

The studies found sleep apnea patients on tirzepatide who weren’t using a CPAP machine had 25 fewer breathing interruptions per hour compared to five fewer breathing disruptions among those taking a placebo.

Among patients using a CPAP machine, researchers found 29 fewer breathing interruptions an hour among patients taking tirzepatide, compared to six who were taking a placebo.

Singh, who was not involved in the clinical trials, said the severity of obstructive sleep apnea is defined by the number of breathing interruptions per hour of sleep.

People with mild sleep apnea generally have about five to 14 interruptions per hour, he said.  Those with moderate sleep apnea have 15 to 30 interruptions and patients with severe sleep apnea have more than 30 an hour, he said.

“A reduction of 25–29 events per hour would represent a meaningful change, potentially shifting someone from severe into a lower severity category depending on where they started,” Singh said.

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“I think that’s a welcome step towards offering, you know, another option for patients who have obstructive sleep apnea,” he said.

There are signs that losing weight on other GLP-1 drugs could also benefit people with sleep apnea, but that’s based on anecdotal observation by clinicians and there isn’t research evidence yet to make that claim, Singh said.

He said more study is needed to see if tirzepatide could have an effect on sleep apnea among patients who don’t have obesity.

“If we can kind of like tease out what is the effect of weight loss versus what is the direct effect of these medications on the upper airway, that will be very interesting.”

The most common side effects of GLP-1 drugs, including tirzepatide, are nausea, vomiting, diarrhea and constipation. More serious but much less likely side effects include inflammation of the pancreas, bowel obstruction and gallstones.

“Whenever a patient is diagnosed to have obstructive sleep apnea, we have a discussion about risks and benefits of the various treatment options available to them. And this medication will go on that list of options when we discuss the risks and benefits,” Singh said.