An allergist and UK clinical guidance disagree on whether daily antihistamines like Zyrtec lose potency over time, and what to do if yours seems to.

"Popcorn brain" isn't a medical diagnosis, but the dopamine-driven attention pattern it describes is one clinicians take seriously. Here's what the evidence actually supports.

For most people, Benadryl brings on sleep. For a smaller group, it brings on racing thoughts and restless legs instead, a documented reaction called paradoxical excitation.

Rust is just iron oxide; it's the soil clinging to an old, outdoor object that carries the bacteria doctors actually worry about when they ask about your last tetanus shot.

Almost half of heat-related deaths happen on a worker's first day. Heat tolerance is not willpower, it is a two-week physiological build with a documented schedule.

The internet's favorite evidence for stacking creatine with magnesium tested a compound most people are not taking. What the trials actually show, and where the safety ceilings sit.

Two of the most-searched calm-down supplements do very different jobs. Here is what the evidence shows, and how to tell which one your sleep problem needs.

L-theanine and magnesium are the internet's favorite sleep supplements. Here is what randomized trials actually found, and which one fits sleep versus anxiety.

Glycinate is calming and gentle; citrate is well absorbed but mildly laxative. Which magnesium fits sleep, constipation and daily use, and what the evidence actually shows.

A single 2009 study on male rugby players still scares women with PCOS away from creatine. Here's what the actual research on women shows about dosing, bloating, and hormones.

Cleanses, cocktails and 'cortisol face' are everywhere online. Endocrinologists say almost none of it works, and the real ways to calm the stress hormone are cheaper and duller than the trend admits.

Two confirmed cases, no deaths, and a health department moving early: what New Yorkers need to know about the Legionnaires' cluster now under investigation on the Upper East Side.

The CDC has confirmed 48 West Nile cases by June 30, far above the usual 10, with Arizona hardest hit as officials urge simple precautions over the July 4 weekend.

With 1,307 confirmed cases and a fourth province affected, the DRC's Bundibugyo outbreak is the fastest first month for Ebola on record in Africa.

A 53% vote closes the longest pay fight in the NHS's recent history, but the doctors' union is already warning it will not stay closed.

The CDC has moved to its highest response level as the Congo-Uganda Ebola outbreak becomes the third largest on record. For US readers, the risk stays low.

A returning aid doctor tested positive in France. The public-health answer to the obvious question is reassuring; the picture inside Congo is not.

The last of 18 Americans exposed to hantavirus on a cruise ship left a 42-day quarantine in Omaha, with federal officials reporting no sustained spread in the U.S.

Teplizumab can hold off the onset of type 1 diabetes for close to three years, but only for the small group caught before symptoms start, and most are never tested.

A second infected seabird put Australia's biggest chicken producer into lockdown. The number that matters, for now, is two.