Repellents, such as insect repellent sprays, help to keep mosquitoes, ticks and other insects at bay and can thus protect against unpleasant bites and, consequently, certain diseases.
The BfR has published FAQs on repellents:
bfr.bund.de/en/service/frequ…
ALT Repelling mosquitoes, ticks and flies: If used incorrectly, certain substances in repellents can cause irritation to the eyes, skin and mucous membranes. The substance DEET is of particular concern in this regard.