Has the formulae of the cheap spray cans of fly killer changed? I/we have not needed to buy any for around 15 years [1], I used the last dregs of it yesterday and it wasn't very effective, but as always it made my eyes water and caught the back of my throat. I bought a fresh can today, tried it and there were not of the anticipated effects, in fact the smell wasn't that unpleasant. I'm not yet sure how effective it was.
[1] During the 'fly season' I fit a fly screen to the inner back door and never open windows during the day, or the unprotected front door - except I was cutting the hedges over the weekend, mostly at the front, so I unlocked and opened the front door to provide a place to sit and take a few minutes rest. The flies must have gained entry then. There is a lot of farmland around me and so flies are a problem.
[1] During the 'fly season' I fit a fly screen to the inner back door and never open windows during the day, or the unprotected front door - except I was cutting the hedges over the weekend, mostly at the front, so I unlocked and opened the front door to provide a place to sit and take a few minutes rest. The flies must have gained entry then. There is a lot of farmland around me and so flies are a problem.