DEET, I find works to some extent, and so does Skin so soft, It smells better and feels better on your skin than DEET.
DEET does melt plastic. I had some spill in a kit bag, same type of material as an Ortlieb pannier, it dissolved the plastic coating of the fabric, and It would not dry. I had to bin the bag.
I don't react well to bites either, horse flies in particular.
What works for me, is a combination of everything. Repellent, cover up with long sleeves and long trousers, wear a mossie net, take anti histamines. Use an after bite stick, ammonia based, supposed to neutralise the stuff the bug injects into you,it stings though. burning mossie coils. Camp where there is a breeze.
Or you could go in the winter