While memory loss is the most recognized symptom of Alzheimer’s disease, new research suggests a much subtler sign may appear first: losing the ability to recognize familiar smells—like your usual shower gel. According to Professor Davangere Devanand of Columbia University, this sensory change could be an early clue of cognitive decline.

Smell is closely linked to memory, and the brain regions involved in scent recognition are often among the first affected in early-onset Alzheimer’s. A long-term study of over 1,000 participants used a simple smell test to detect warning signs. People were asked to identify 12 common scents—like soap, smoke, rose, and leather. Those who scored under 8 were significantly more likely to develop cognitive impairment.

This test, especially when paired with a short memory check, was found to be as predictive as an MRI or more complex evaluations. Better yet, it’s non-invasive, affordable, and could be performed during routine doctor visits.

Key scents to note: soap, gas, lilac, lemon, cherry, and menthol. If you consistently fail to recognize several of these—especially a once-familiar scent—it may be worth consulting your doctor.

Sometimes, your shower could tell you more about your health than you think.