I usually get badly bitten if there are any mosquitoes at all. In May I visited Antigua (which is known for having lots of mosquitoes) where it rained a lot during the week I was there - ideal mosquito weather. However, using this spray I was bite-free at the end of the week, unlike other people who got plenty. I also liked having a product with no Deet - no worries about toxicity or the annoyance of melted plastic items.
It has quite a strong smell but you stop noticing it quite quickly. It seems to protect against sand flies too as there were plenty about but no bites on me. I put it on twice a day - first thing in the morning and just before dinner. I'm doing this review because I'm back on this page buying some more! (A bottle lasts one person about 2 weeks of daily use)