What happened with my homemade bug repellent?

Ok so I’m currently living in Costa Rica, needless to say mosquitoes, sandflys and other biting insects are a bit of an issue. I don’t really like the idea of using DEET or other chemicals to repel them and it’s too bloody hot to wear layers so I’ve been making my own bug spray.

Normally what I do is boil lime zest, rosemary, basil, and mint to extract what I can from them and then add some aloe to the finished mixture. It’s been working for me quite well, better than the store bought bug spray actually.

This last batch I decided to add rubbing alcohol to the mix as that helps a ton with areas that are already itching. To my surprise when I added the rubbing alcohol the whole mixture congealed.

What caused this to happen?