Sorry to hear that your skin rashes are breaking out all over.
Sandfly or insect bite reaction is due to a hypersensitivity response of your body to the insect bites. In susceptible individuals, the body mounts a hypersensitive or ‘allergic’ response to the foreign protein deposited in the skin from the bite. The reaction can persist for weeks to months after the initial insect bite.
People with atopy (ie asthma, eczema or allergic rhinitis/sinus) may be more susceptible to insect bite reactions.
It is certainly possible for this hypersensitivity response to the insect bites to trigger eczema, and make you more susceptible to the rashes and outbreak you are experiencing, especially given your history of sensitive nose and sinus.
I think you should continue with general measures to prevent rashes and eczema, like using gentle soap-free cleansers and moisturizers regularly.
Avoid scratching, which can aggravate the rash. If the rash is still not well controlled or flaring, you can see your dermatologist/doctor to help control your condition.