I have noticed (and large inflamed lumps do get my attention quickly!) a huge increase in clegs here this summer, I assume it's the prolonged dry heat..
The only thing works for me is taking antihistamines, cetirizine hydrochloride unbranded from the chemist 10mg is the best and cheap for having no brand name over it - plus it's a non-drowsy making one so safe to take before finishing with anything that requires attention, from driving and machinery to just animal handling.. I also have Pollenase which is 4mg chlorphenamine maleate but it does make you drowsy and can't be taken if you plan a drink in the evening either, so I no longer use it for preference.
Anything on the skin washes off with sweat or water in this hot weather, gets rubbed off by dirt, animals etc or fades so quickly it doesn't deter a housefly let alone a cleg

Couple of days last week I got half a dozen cleg bites within a couple of hours, so the tablets were a godsend.