Is “A Little Waterproof Spray Is Nothing to Worry About” Just an Assumption? What Recent Insights Teach Us About Rainy-Season Waterproof Spray and Proper Use

During the rainy season, many people apply waterproof spray to shoes, raincoats, and bags. It's a habit most of us do every year without a second thought — but a respiratory medicine clinic in Shizuoka Prefecture is warning that using it the wrong way can unexpectedly make you unwell. Here's a helpful perspective for midlife readers and beyond, drawn from that clinic's explainer.

Why Waterproof Spray Can Sometimes Affect the Body

• Symptoms don't necessarily appear right after use — they can show up hours later as coughing or shortness of breath, the explainer notes. Because this can be mistaken for “maybe I'm coming down with something” or “maybe I'm just tired,” the clinic advises keeping track of when and what you used.
• Using it in poorly ventilated spots such as entryways, closets, or bathrooms calls for particular caution, the explainer states. Fine particles can linger in the air in such spaces, potentially increasing the amount inhaled.
• Smoking right after using the spray is best avoided, the explainer notes. Heat can alter the spray's components, potentially increasing its effect on the body.

Small Precautions You Can Take in Daily Life

According to this clinic's explainer, the goal isn't to avoid waterproof spray altogether — a few small adjustments to how you use it can meaningfully reduce the risk. The following commonly recommended tips may offer a starting point.

• Spray outdoors in a well-ventilated spot, holding the item about 30 cm away
• After spraying, step away from the area for a while before returning indoors
• If coughing or shortness of breath continues after use, don't push through it — consult a medical institution promptly

* The above are commonly recommended lifestyle habits and do not guarantee improvement, treatment, or prevention of any specific condition.

Last updated: July 13, 2026