Silicone is a heavy and non-breathable material, which can be a burden on the breasts when it is attached to them. Furthermore, if worn for long periods of time, the breasts are not only impermeable to air but also allow sweat to accumulate in them. This makes it particularly easy for bacteria to grow and irritate the skin, leading to constant itching of the breasts. Some people are allergic to the silicone material and experience itching.