Can a B12 Deficiency Cause Hair Loss? Yes, but Only Through Specific Mechanisms
Yes, a B12 deficiency can cause hair loss, but the evidence supporting this link is mostly indirect.
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Ideas for a curious mindMind & Body
Can a 2 Month Old Go to the Mountains? A Physiology-First Guide to Altitude, Cold, and Timing
A 2 month old can travel to the mountains, but not to every mountain.
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Can Your Vagina Swell? Yes — Here's the Anatomy and Physiology Behind It
Yes, your vagina can swell. Swelling (edema) can affect the vaginal walls, the vulva, or both, and it happens when fluid collects in tissues or when blood flow to the area increases. Most episodes are temporary and harmless.
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Can Your Toes Fall Off From Poor Circulation? The Vascular Science Behind Tissue Death
No, toes do not spontaneously detach from poor circulation alone. What actually happens is tissue necrosis, in which skin and underlying tissue die and may eventually slough away, leaving a non-healing wound or exposed bone.
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Can Your Skin Reject Tattoo Ink? What Immunology and Dermatology Actually Say
Yes, your skin can reject tattoo ink, but true rejection is uncommon and looks different from what most people imagine. The immune system treats pigment particles as foreign debris and constantly works to clear them.
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Can Your Period Affect a Urine Test? Yes, and Here Is Exactly Which Results Shift
Yes, your period can affect a urine test, though the size of that effect depends on the test. Menstrual blood can contaminate a urine sample with red cells, protein, and hemoglobin. It can also add bacteria and alter pH.
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Can Your Period Cause Swollen Lymph Nodes in Groin? A Mechanistic Deep Dive
Yes, a period can cause swollen lymph nodes in the groin, but only indirectly and rarely as the sole symptom.
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Can Your Period Cause an Eczema Flare-Up? Yes, and the Mechanism Is Stranger Than Hormones Alone
Yes. A period can trigger or worsen an eczema flare-up, and the effect runs through the menstrual cycle rather than the bleed itself.
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Can Your Ovaries Hurt After a Hysterectomy? What Pelvic Pain Really Means
Yes, your ovaries can hurt after a hysterectomy, and the pain has several distinct causes.
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Can Your Labrum Repair Itself? The Biology, Limits, and Clinical Reality
No, a torn labrum cannot repair itself. The labrum is a ring of fibrocartilage around the shoulder or hip socket, and fibrocartilage has almost no blood supply in its inner two-thirds.
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Can You Wear Contacts With a Popped Blood Vessel? A Complete Safety Guide
You can usually keep wearing your contacts after a popped blood vessel, but only if the bleed sits on the white of the eye, your vision is normal, and there is no pain or discharge.
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Can Your Immune System Fight Off Herpes? Yes, But It Cannot Clear It
Your immune system can fight off herpes outbreaks, but it cannot eliminate the virus. It suppresses herpes simplex virus (HSV) replication, shortens outbreaks, and forces the virus into latency.
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Can Your Lip Get Infected From Biting It? Yes—Here's Exactly How It Happens
Yes, your lip can get infected from biting it. The mouth contains hundreds of bacterial species, and a bite that breaks the lip's protective barrier lets oral flora invade deeper tissue.
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Can Your Jaw Hurt From Talking Too Much? The Science of Jaw Overuse
Yes, your jaw can hurt from talking too much. Sustained speaking loads the temporomandibular joints, the masseter and pterygoid muscles, and the trigeminal nerve pathways that relay their signals.
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Can You Use the Same Needle to Draw and Inject? The Short Answer Is No
No. You should not use the same needle to draw medication and then inject it, with narrow exceptions. Reusing a draw needle for injection dulls the tip, raises contamination risk, and makes the injection more painful and less precise.
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Can Your Genes Change? How DNA Itself Changes and How Your Body Rewrites Its Readout
Yes, your genes can change. Some changes are hardwired into the DNA sequence and last a lifetime. Others are chemical marks that switch genes on or off, and those marks shift with age, diet, stress, and environment.
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Can Your Hair Color Change Naturally Over Time? Yes — Here Is the Biology Behind It
Yes. Hair color can change naturally over time, and it does so through distinct biological routes: pigment production inside the follicle, structural changes in the hair shaft, and shifts in the pigment ratio itself.
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Can Your Bowels Cause Back Pain? What the Gut-Spine Axis Really Explains
Yes, your bowels can cause back pain, but only through a narrow set of mechanisms, and they account for a small fraction of back pain overall. The colon and rectum share nerve supply and physical space with the lower back.
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Can Your Body Fight Off a Small Amount of HIV? Here Is What Immunology Says
No. The human body cannot reliably fight off even a small amount of HIV, and that answer holds for every exposure route scientists have studied.
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Can You Wear a Bunion Corrector With Shoes? A Guide to Fit, Forces, and Foot Health
Yes, you can wear a bunion corrector with shoes, but only if the shoe has enough internal volume to accommodate both your foot and the device. Most standard shoes fail this test.
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Can You Walk With a Torn Ligament in Your Ankle? A Mechanistic Guide
Yes, most people can walk with a torn ankle ligament, and many do so within days of injury. Walking is not the same as healing, though.
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Can You Vape With Asthma? The Physiology, Risks, and Harm-Reduction Reality
Yes, you can physically vape with asthma, but doing so is not safe and no respiratory or medical authority endorses it.
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Can You Walk With a Fractured Pelvis? A Deep Dive Into Load, Stability, and Healing
Yes, in some cases a person can walk with a fractured pelvis, but only when the break is a stable, minimally displaced pattern that does not threaten the ring's integrity or nearby organs.
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Can You Use a TENS Unit With a Pacemaker? No, Unless Cardiology Confirms Otherwise
No. You should not use a TENS unit if you have a pacemaker or an implantable cardioverter-defibrillator (ICD), because the electrical current can interfere with the device.
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