Thanks for informing me about your health concerns.
The fact is that your skin is rather sensitive. This is because people from temperate zones do not have the necessary skin defenses to deal with the rather harsh conditions obtained in the tropics.
Mosquito's in the tropics have now mostly become resistant to repellents. Your skin gets pricked with a mosquito's "proboscis" once you are bitten by one. The saliva of the mosquito carries germs (naturally) and some chemicals called "antigens". These "antigens" cause your immune system to immediately respond. This causes swelling,
redness and itching which is called as "inflammation" that leads your
insect bites to "weep".
I think you have an "allergy" to the mosquito's in the vacation spots that you frequent.
This is because there are many different kinds of mosquito's in different parts of the world.
I advise you to kindly ask a physician to give you "anti-histaminic" pills, and a local steroid-antibiotic combination ointment to apply to your insect bites.
The "anti-histaminics" will stop your skin from over reacting, the steroid in the ointment will speed up the healing process, and the antibiotic will eliminate infections if any.
In the tropics, you can find many products to repel further, and outright kill
nasty mosquito's. There are vaporizors and neon electrocutor traps, and various perfume grade aerosols that eliminate the pests.
I suggest that you wear fine cotton wear that would keep you cool and
would prevent insect stings.
Please feel free to inquire about any other health problems.