Yeah, tough one Flopen. As many have pointed out.
However, I feel you should pursue the matter. The little person's health and wellbeing is too important to let it go. At the other end of the seesaw, your friendship with DIL is too important for fornicate it up with a clumsy go at getting your point across. Is that fair enough?
How about waiting until a neutral time? Say when DIL and you sit together chatting over a cup of coffee?
At which point you raise the subject of the effect of household products on say . . . Now, I don't know where your DIL's interests lie. Global warming and health are both popular subjects, so how about starting with her ideas on global warming, making sure you listen more than you talk, and then work round to household sprays and health making sure once again that you listen more than you talk.
Now, the tricky point for me is err um . . .
As a Newby, I'm not too sure how to put this, but are you completely sure that the way you said what you said in your letter is more likely to make hate than love.?
Will others dig me out the hole I've just dug for myself please?