Is it harmful to humans if the buffer solution from a self-testing COVID-19 antigen kit is applied into the nasal cavity?

Generally, whether the elution solution from a COVID-19 antigen self-testing kit is harmful when applied to the nasal cavity depends on the specific circumstances of exposure. The detailed analysis is as follows:

If only a small amount of elution solution briefly contacts the nasal cavity and is promptly rinsed with clean water, and no discomfort such as redness, swelling, or stinging occurs, it typically does not cause significant harm. The main component of the elution solution is a buffer solution. Although it is not specifically designed for nasal mucosa, its irritancy is low upon brief, limited contact. Timely cleaning helps reduce residue, while the body's natural mucosal barrier also provides some protection. In such cases, there is generally no need for excessive concern—simply monitor for any nasal reactions afterward.

However, prolonged exposure to a large amount of elution solution, or contact in individuals with sensitive or damaged nasal mucosa, may trigger irritation symptoms such as nasal congestion, runny nose, or burning pain. In such cases, the nasal cavity should be thoroughly rinsed immediately with normal saline. If symptoms persist or worsen, the mucosal barrier may become compromised, increasing the risk of infection. Medical attention should be sought promptly; do not ignore or neglect these symptoms.

Handle testing kits carefully to avoid spilling the elution solution. If accidental nasal contact occurs, rinse immediately with clean water or normal saline. Store test kits out of reach of children, and seal the packaging promptly after use. Maintain clean and moist nasal passages, avoid frequent picking with fingers, minimize the risk of mucosal damage, and support overall nasal health.