If you experience contact dermatitis due to your skin's reaction to either a product or environmental issue, you could either (1) try an 'elimination diet' with all of the products that touch your skin to discover which one (or more than one) caused the rash, or (2) dump all 'regular' commercial products in the trash bin and start over with natural or 'green' products that do not contain chemicals which can cause dermatitis even in skin that is not sensitive.
I have sensitive skin as well as respiratory allergies and have gradually replaced all of the commercial products I once used for natural (and these are usually inexpensive, such as vinegar, hydrogen pyroxide, baking soda, water, etc.) and 'green' (these cost more, but I use less and don't waste even a drop) products without harmful chemicals.
I searched all over the Internet to find a single toothpaste (made by miessence in Australia) that doesn't contain parabens. There are also websites that list personal care products that are healthier/safer, and some of them show how to find the least expensive. It's a lot of work, but it's for your health so that makes it worthwhile. This is especially important if it's needed for children.
I wash bed linens, towels, underwear, etc. with one of the mild 'green' non-detergent cleaners and vinegar. I rinse each load a second time with cold water, and I don't use dryer sheets (notorious for causing contact dermatitis). Good luck with your quest!