I've just posted on another thread today that estrogel is the only transdermal oestrogen that suggest upper arms and shoulders to apply as well as lower trunk. Sandrena gel and all the patches say on the lower half of the body, as does tesosterone gel (well the patches that were for women did and I was told to). I just presume that this minimises the chance of any being transported close to the breasts but as I said on the other thread if it says it's OK for estrogel then it must be!
Kathleen there was a study that showed absorption was reduced when estrogel was spread as thinly as possible ie the largest possible area - and I presume this is because it dries too quickly before it can be absorbed. However there was no difference in absorption in the other two sized areas they studied. Sorry don't have the paper to hand! I haven't used estrogel although I do use testosterone gel - but only a small amount.
As I also mentioned on the other thread saturation is fine (according to another paper I read) as the oestrogen builds up in the skin and provides a reservoir to transport it - into the blood stream. For example Sandrena gel says simply alternate between right and left inner thigh - but estrogel says nothing about the same or different sites or rotating it.
I think the main thing is to find a way of applying it that works for you and relieves your symptoms and then stick to it - so you get less variation in oestrogen levels? Floundering a bit here!
Hope it works anyway
Hurdity x