The symptoms you describe are most commonly due to nasal allergies. In mild cases, you can ask the pharmacist for an antihistamine (allergy medication), which can be purchased without prescription.
The older anti-histamines cause drowsiness but most of the newer antihistamines can be safely taken without making you feel sleepy.
If you constantly need to take antihistamines more than four times a week, you may want to seek a specialist consult for better control.
The other practical thing you can do is to try to avoid likely allergens. In Singapore, 80 to 90 per cent of allergies are due to house dust mites. They thrive in our warm and humid climate and are commonly found in beddings, blankets, pillows, bolsters and mattresses.
You should avoid covering your nose with pillows/blankets, and avoid sleeping face down. Sheets should also be washed at least once a week, preferably with hot water (more than 60 deg C), and old pillows/bolsters should be changed yearly.
Dust mite treated mattresses and pillows are commercially available at reasonable prices. There are also medical grade dust mite proof covers and anti-dust mite sprays, but you might only want to invest in these only after proper assessment as they can be quite costly. You should also avoid too much clutter on and around the bed, including soft toys, cushions and books.