I've recently started using a primer, for about 2 weeks now, and I don't think it's made me break out any more than usual.

I was worried that it might as my skin tends to when I use a new product but so far so good! If anything I've found that it helps since it keeps my makeup on I don't have to pile any more on through the day which must be better for my pores.

It might depend on the quality of the primer you use. I use Benefit and compared to some others I've tried in the past is very good quality.

You could try applying the primer to just one side of your face and see if you break out there.

I'm not sensitive to dimethicone in particular, but so many of those primers have a multitude of silicones in 'em. I'd recommend picking up products that list fewer types of silicone and shorter ingredients lists. I've had much better luck with them.

I've been using Tarte's BB Tinted Primer for a couple of weeks with no problems so far. It has SPF 30 in it, too!

Silicones or other occlusives don't do well on my skin. When I wear makeup it's for 6+ hours. Having an occlusive like a primer sit on my skin is like saran wrap. My skin is pretty dry but with a primer, silicone-based sunscreen or silicone-based foundation, my face becomes an oil slick and the makeup melts off.

I think primers are overrated and really only suited for 40+ skin that is super dry.

Primers are dirt cheap to make, I think Smashbox's primer costs a total of $1 to make and they sell it for $40

There are silicone-free primers if you are worried about silicone-induced breakouts. I have used Sephora's silicone-free primer in the past. Costs about $15 and it did help keep my make-up on for a longer period of time, though it didn't really help even out the skin's surface like other primers (with silicone) might do.