Pick up almost any medicine box and turn it over. Somewhere in the small print you will find it: store below 30 °C, store in a dry place, protect from moisture, keep the container tightly closed.
Those words assume a dry storeroom. In much of Sri Lanka, for much of the year, the air in an ordinary room is anything but.
Why does humidity matter for medicines?
Some medicines and medical products are sensitive to moisture. Effervescent tablets, some capsules and powders, and diagnostic test strips are well-known examples, and many labels specify protection from moisture alongside a temperature limit. Damp storage also attacks the packaging — softening cartons, smudging labels and leaflets, and encouraging mould. That is why international good-storage guidance from the World Health Organization expects storage areas to be kept within the conditions on the label, and monitored.
The responsibility sits with whoever stores the product: the importer, the distributor, the pharmacy, the clinic. In Sri Lanka, the National Medicines Regulatory Authority (NMRA) regulates medicines and the premises that handle them.
“Store in a dry place” is an instruction, not a suggestion — and in a monsoon storeroom it takes active effort to obey.
Which medicines are most sensitive to humidity?
| Product | What moisture can do |
|---|---|
| Effervescent tablets and sachets | Absorb moisture and start reacting inside the pack |
| Some capsules | Soften, stick together or deform |
| Powders and granules | Clump and become hard to dose |
| Diagnostic test strips | Strip vials opened in damp air can give unreliable readings |
| Cartons, labels, leaflets | Soften, stain, smudge and grow mould spots |
| Medical devices and dressings | Packaging damage, compromised seals |
Always defer to the product’s own label and the manufacturer’s information for its specific requirements.
Why do pharmacies struggle to keep medicines dry?
- Stockrooms behind the counter are often small, closed and not air-conditioned at night.
- Shop doors open all day to 80–90% outdoor humidity.
- Air-conditioning controls temperature during opening hours, then switches off — and humidity rises overnight.
- Deliveries sit in loading areas and vans before reaching the shelf.
- Cardboard outer cartons stacked on floors wick up moisture.
How should a pharmacy store medicines in a humid climate?
Follow each label, monitor temperature and humidity with recorded readings, keep the store room closed and dehumidified around the clock, and keep stock off floors and walls.
- Read the label for every product line and group stock by storage condition.
- **Monitor temperature and humidity** with data-logging thermo-hygrometers, and keep the records — WHO guidance emphasises monitoring.
- Keep the store room closed, off the shop floor’s door traffic.
- Control humidity around the clock, not just in opening hours. A small store room suits a 20 L/day unit such as DRYAir’s DA-20L; a larger dispensary or distributor’s store the DA-35L with continuous drainage.
- Get stock off the floor and away from outside walls.
- Keep containers tightly closed — especially test-strip vials and multi-dose bottles.
- First expiry, first out — the less time on a damp shelf, the better.
- Check for damage on receipt and quarantine damp or stained stock.
The bottom line
Pharmacies and clinics in Sri Lanka are storing products that were designed and tested with a dry, controlled storeroom in mind. Keeping that promise in 80% humidity takes monitoring and active humidity control. A properly dried, logged store room protects the products, the business and the patients who rely on them. DRYAir supplies commercial store rooms across Colombo — see the range or get in touch. For the wider business picture, see how humidity destroys shop stock.
Questions readers ask
Does humidity affect medicines?
It can. Some medicines and medical products are sensitive to moisture — effervescent tablets, some capsules and powders, and diagnostic test strips are common examples — which is why labels often say to store in a dry place or protect from moisture. Damp storage can also damage cartons, labels and leaflets. Always follow the storage conditions on the label and the guidance of your regulator.
What humidity should a pharmacy store room be kept at?
Follow the storage conditions stated on each product and your regulator’s requirements. In practice, keeping a pharmacy store room at a controlled temperature and below about 60% relative humidity, with readings recorded, makes it much easier to meet “store in a dry place” instructions in Sri Lanka’s climate.
Sources
- World Health Organization — TRS 1025, Annex 7: Good storage and distribution practices for medical products (2020)
- World Health Organization — TRS 961, Annex 9: Model guidance for the storage and transport of time- and temperature-sensitive pharmaceutical products
- National Medicines Regulatory Authority, Sri Lanka — NMRA — regulator of medicines in Sri Lanka
- US Environmental Protection Agency — A Brief Guide to Mold, Moisture and Your Home
Guidance from these bodies is general; figures for Sri Lanka come from our own reporting and DRYAir’s field experience.
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