Hopefully you will enjoy some sunshine and so for most people a high factor sun cream and after sun lotion is important. For touring the sights or even lazing on the beach or by the pool you might want to consider wearing a hat or cap for added protection
Mosquitoes are widespread. It’s possible to purchase ointments for bites from pharmacies in Sri Lanka (and a good natural remedy is aloe vera)
Prevention is better than cure and you are advised tobring a repellent spray such as “Jungle Formula”
If you take prescription medication ensure that you bring sufficient quantity for the duration of your stay
You may wish to bring some toiletries as deodorants, shampoo, shower and body gels are expensive and you may not be able to find your favourite brand
There can be occasional power outages (most hotels etc. have standby generators) A torch can be handy or download a flashlight app on to your mobile/cell phone
An international electric adaptor for recharging your personal devices (mobile/cell phones,tablets and lap tops etc.) is necessary and a spare charged battery can prove useful