10 Strange Signs of Common Conditions

No one wants to get sick—whether it’s the common cold or a rare condition that sounds like a spelling mistake. Unfortunately, illness is a part of life, and at some point, we all find ourselves sneezing, aching, or reaching for a thermometer. For the most part, we expect certain symptoms with familiar conditions: a runny nose with a cold, a sore throat with strep, or fatigue with the flu. But sometimes, even the most common ailments can throw you a curveball with symptoms that are just plain strange.

Here are 10 bizarre symptoms of common conditions that might leave you scratching your head—or in one case, smelling burning toast.

1. Cold Weather Causes Sneezing (Photic Sneeze Reflex)

Condition: Common cold or bright sunlight exposure
Bizarre Symptom: Sneezing uncontrollably when stepping into the sun

While sneezing is expected with a cold, some people experience a strange phenomenon where stepping out into bright sunlight causes them to sneeze. This is known as the photic sneeze reflex, and while not caused by illness directly, it often appears during colds or allergies when your sinuses are more sensitive.

The exact cause is unknown, but it’s believed to involve a crossed wire in the brain between the optic and trigeminal nerves. About 10-35% of people are estimated to have this reflex—so if you’ve ever sneezed in direct sunlight, you’re not alone.

2. Appendicitis Can Cause Pain… in the Shoulder

Condition: Appendicitis
Bizarre Symptom: Referred pain in the right shoulder

Appendicitis is known for causing sharp pain in the lower right abdomen. But in some rare cases, it can also lead to pain in the right shoulder. This happens because of referred pain, where pain from one part of the body is felt in another due to shared nerve pathways.

This shoulder pain can be caused by irritation of the diaphragm due to the inflamed appendix or abdominal pressure—especially if the appendix has ruptured. It’s a rare symptom, but one that doctors are trained to look out for.

3. Urinary Tract Infections Can Cause Hallucinations

Condition: Urinary tract infection (UTI)
Bizarre Symptom: Hallucinations or confusion

UTIs are incredibly common, especially in older adults, and we usually associate them with painful urination, urgency, and lower abdominal pain. However, in elderly individuals, a UTI can sometimes present without any typical urinary symptoms at all. Instead, it can cause delirium, confusion, or even hallucinations.

The reason is that infections in older adults can trigger systemic inflammation or disrupt brain function due to decreased immune response. If your normally sharp grandparent suddenly seems confused or disoriented, it might not be dementia—it could be a hidden UTI.

4. Heart Attacks Can Cause Jaw or Tooth Pain

Condition: Myocardial infarction (heart attack)
Bizarre Symptom: Pain in the jaw, neck, or teeth

We tend to think of heart attacks as involving dramatic chest-clutching moments. But sometimes, the only symptoms might be pain in the jaw, neck, or even the teeth. This is another example of referred pain, where the nerves in the heart share pathways with other parts of the body.

This is especially common in women, who are more likely to have atypical heart attack symptoms. If you experience unexplained jaw or tooth pain along with shortness of breath or fatigue, don’t ignore it—seek medical attention immediately.

5. Diabetes Can Cause Sweet-Smelling Breath

Condition: Diabetes (especially Type 1)
Bizarre Symptom: Breath that smells fruity or sweet

People with uncontrolled diabetes can develop a condition called diabetic ketoacidosis (DKA). When the body can’t use glucose for energy, it starts breaking down fat, producing ketones—a type of acid—as a byproduct.

One of the symptoms of DKA is fruity or sweet-smelling breath. It’s a result of the body trying to expel excess ketones through the lungs. While it may not sound alarming, this symptom can indicate a serious and potentially life-threatening condition requiring urgent treatment.

6. Migraine Can Cause Visual Hallucinations Without Pain

Condition: Migraine
Bizarre Symptom: Visual distortions like zigzags, flashing lights, or blind spots

Migraines are notorious for their blinding pain, but not all migraines come with a headache. Some people experience “silent migraines” or migraine with aura, where visual disturbances occur without any pain.

This might include flashing lights, shimmering patterns, or even temporary vision loss. While disorienting, these auras are usually harmless and pass within 30–60 minutes. However, they can mimic signs of a stroke, so they should be evaluated by a doctor if they’re new or unusually severe.

7. Mononucleosis Can Cause Swollen Eyelids

Condition: Mononucleosis (Mono)
Bizarre Symptom: Puffy or swollen eyelids

We think of mono as the “kissing disease” that causes fatigue, sore throat, and swollen lymph nodes. But some people—especially teens—also develop eyelid swelling early in the illness. It can look like a bad night’s sleep or allergies but is actually due to inflammation caused by the Epstein-Barr virus.

This lesser-known symptom often appears in the first few days and can help doctors identify mono before the more classic signs emerge.

8. Strep Throat Can Cause a Rash (Scarlet Fever)

Condition: Streptococcal infection
Bizarre Symptom: A red sandpaper-like rash

Strep throat doesn’t just affect the throat—it can also affect your skin. Sometimes, the bacteria that cause strep throat (group A Streptococcus) also lead to a condition called scarlet fever, where a rough, red rash appears on the body.

This rash feels like sandpaper and usually begins on the chest before spreading. It’s more common in children, but adults can get it too. It might look alarming, but with antibiotics, it typically clears up without long-term effects.

9. COVID-19 Can Cause Loss of Smell and Taste

Condition: COVID-19
Bizarre Symptom: Sudden loss of smell (anosmia) and taste

One of the most peculiar symptoms of COVID-19 is the sudden and complete loss of smell and taste—often without nasal congestion. This became one of the hallmark signs of early COVID-19 infections and sometimes the only symptom people experienced.

The virus affects the nerve cells responsible for smell, leading to a temporary (or sometimes prolonged) loss of sensory perception. For many, this symptom fades over time, but in some cases, it can linger for months.

10. Anemia Can Cause Restless Legs Syndrome

Condition: Iron-deficiency anemia
Bizarre Symptom: Crawling or tingling sensations in the legs

Iron-deficiency anemia is usually associated with fatigue and pale skin. But it can also cause restless legs syndrome (RLS)—a condition where individuals feel an uncontrollable urge to move their legs, often accompanied by tingling, crawling, or prickling sensations.

The connection between low iron and RLS isn’t fully understood, but iron plays a role in dopamine production in the brain, which is involved in motor control. Treating the anemia often reduces or eliminates these creepy-crawly leg sensations.