Explore questions from across science through evidence, mechanisms, limitations, and the explanations behind familiar claims.
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Levothyroxine itself does not usually cause brain fog. When cognitive symptoms appear or persist on levothyroxine, the cause is almost always one of four things: the dose is too low (under-replacement), the dose is too high…
Read the story ↗Yes, lack of sleep can cause swollen eyelids, and the effect is usually mild, temporary, and fluid-driven rather than allergic.
No, L-theanine is not an established cause of depression, and no controlled human trial has reported it as a causal effect.
Yes, knee valgus can be corrected in most people, but the mechanism that fixes it is not the one most programs sell you.
Yes, kratom can cause heart problems, and they fall into four distinct categories: short-term stimulant effects, blood pressure and rhythm changes, rare cardiac events in susceptible users, and indirect harm from contaminants or withdrawal.
Yes, kids can do Pilates, and most school-age children benefit from it when the program is scaled to their body size, maturity, and stage of growth. Children roughly ages 5 to 7 can handle short mat sessions built around games and balance.
Yes, kittens can get toxoplasmosis from their mother, but only during a narrow window that opens about two weeks before birth and closes around three weeks after it. Transmission happens in two ways.
Yes, lactose intolerance can cause frequent urination, but almost never through a direct effect on the bladder.
Yes, kidney stones can cause bloating, but almost never directly.
Yes, kratom can cause psychosis, but it is uncommon and almost always occurs under identifiable conditions: very high doses, chronic daily use, withdrawal, or use combined with other stimulants or in people with a bipolar or…
Yes, kids can get skin tags, but it is uncommon before puberty.
Yes, kittens can go outside, but not before roughly 16 weeks of age and only after completing their core vaccine series, microchipping, and parasite prevention.
Jock itch (tinea cruris) can cause swollen lymph nodes, but only in a minority of cases and almost always when the fungal infection has spread beyond the skin surface.
Yes. Chronic kidney disease (CKD) is one of the most common and most underdiagnosed causes of anemia, and it is a direct, mechanistic consequence of losing kidney tissue rather than a coincidence of chronic illness.
Can kidney problems cause swollen lymph nodes? Yes — but only through specific pathways, not as a general rule. Kidney disease itself does not inflate lymph nodes the way strep throat or a respiratory infection does.
Yes, jelqing can cause erectile dysfunction and nerve damage, though the risk is dose-dependent rather than universal.
Yes, infection can cause elevated troponin, and it does so far more often than most people realize. Troponin is a structural protein in heart muscle cells, and it leaks into the blood whenever those cells are injured, stressed, or dying.
Yes, intermittent fasting can cause hypoglycemia, but mainly in people whose glucose regulation is already compromised.
No, infrared light is not known to cause skin cancer directly, because it lacks the photon energy to damage DNA the way ultraviolet radiation does.
Yes, insulin can cause diarrhea, but it is an indirect cause rather than a direct one.
Yes, indigestion can cause upper back pain. Acid reflux and dyspepsia frequently produce referred pain between the shoulder blades because the esophagus and stomach share nerve pathways with the upper back through spinal segments T4 to T10.
Yes, insulin can contribute to depression, but almost never on its own.
Yes, indigestion can cause headaches, though usually indirectly.
Ibuprofen does not usually cause back pain, but it can contribute to chronic pain through two well-documented pathways.
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