Blister packaging for hot and humid markets

Conditions for zones II, IVa and IVb from WHO Technical Report Series No. 1010 (2018), Annex 10, a guideline written for medicines, which describes climatic zone IV as hot and humid.

Which climatic zone is my market in?

It is set by the country where the product will be sold, not where it is made: WHO's stability guideline ties the long-term condition to the climatic zone of the market the product is intended for.

Hot does not always mean zone IVb. In WHO's list of stability conditions by country (update of March 2021), Nigeria, Ghana, Cameroon and Tanzania are given a long-term condition of 30 °C/75 % RH, which corresponds to zone IVb. Saudi Arabia, the United Arab Emirates and Egypt are given 30 °C/65 % RH, which corresponds to zone IVa, and Lebanon 25 °C/60 % RH. Egypt's drug authority also places the country in zone IVa in its own stability guideline, and Ghana's Food and Drugs Authority names WHO zone IVb conditions in its guideline for supplements.

Read the list with its limits. It records the conditions WHO Member States require when a medicine is registered, so for a supplement it is a reference frame rather than law. WHO marks how each entry was obtained: those for Saudi Arabia, the UAE, Egypt and Lebanon come from regional harmonisation groups or official communications from national regulators; those for Nigeria, Ghana, Cameroon and Tanzania were collated at a conference of drug regulators in 2008; entries in square brackets are an industry association's estimates from climate maps, not statements by a regulator. The list gives conditions rather than zone names; the zone follows from WHO's note that zone IVa is 30 °C/65 % RH and zone IVb is 30 °C/75 % RH. We found no edition later than March 2021. Our country page lists 23 countries in the Gulf, the Levant and Africa, each with a note on how WHO obtained the entry.

The scheme runs from zone I to zone IVb; this page gives the conditions for zones II, IVa and IVb. The ICH stability guideline, Q1A(R2), addresses climatic zones I and II, and 30 °C/65 % RH appears in it both as a long-term option and as the intermediate condition. ICH left the conditions for zones III and IV to the regions and to WHO, and its regulators agreed that the stricter 30 °C/75 % RH is acceptable when an applicant chooses to use it.

Both documents are written for medicines. As far as we found, neither is binding on a food supplement by itself: one regulator writes stability conditions into its supplement guideline, another names none, as the regulator table further down shows.

Why does the pack decide how much humidity reaches the product?

Because zones IVa and IVb share the same 30 °C and differ only in humidity, and the pack sets how much of that humidity reaches a tablet or capsule.

WHO puts it in its own terms. Sensitivity to moisture, its guideline says, is not a concern for products in impermeable containers that give a permanent barrier to moisture, and studies of such products can be run at any controlled or ambient humidity. The same guideline says zone IVa data may be acceptable in place of zone IVb when humidity is not an issue, giving storage in glass containers as its example.

The label cannot make up for the pack. WHO states that a storage statement should not be used to compensate for inadequate or inferior packaging, and warns that testing at zone I or II conditions for a product supplied to zones III and IV could lead to substandard products.

The formula still counts: a product that readily takes up moisture asks more of its pack than one that does not. The pack, not the dose, decides how much of that humidity reaches the product, and in a blister the barrier comes from the film and the lidding foil.

How does a blister protect each dose?

Each tablet or capsule sits in its own cavity under the lidding foil, so pressing out one dose leaves the rest sealed.

In a bottle, every opening lets room air reach all the doses still inside. WHO's guidance for medicines uses a 500-tablet HDPE bottle as its example of a moisture-sensitive product in a large multidose container, and treats an in-use period of 30 days as normally acceptable without further supporting data.

Until a cavity is opened, how much moisture crosses its wall depends on the film. The figures below are water vapour transmission rates (WVTR) that film suppliers publish for flat film.

Read the table with three limits in mind:

• Compare rows only where the condition and the source match. The three PVC/PVDC rows share one source and 38 °C/90 % RH, so they can be read against each other as the effect of coating weight within that source. We do not have the thickness of the PVC base under these coatings, so the rows are not values for PVC/PVDC film in general. The PCTFE row is for PCTFE film on its own, measured at other conditions, and cannot be set beside them.
• The values describe flat, unformed film. An article by an engineer at a packaging manufacturer notes that forming a cavity makes the laminate thinner, which can lower its barrier, and that the barrier of aluminium is independent of its thickness. In cold-formed aluminium blisters, the same article adds, a very small amount of water vapour may enter through the punched edge.
• They are suppliers' figures, not measurements of blisters from our line.

If the same product is also sold in the EU, the PCTFE row raises one more question. Since 12 August 2026, Regulation (EU) 2025/40 has limited PFAS in food-contact packaging placed on the EU market. PCTFE is a fluorinated plastic. Whether a given PCTFE laminate meets that limit, and how the limit applies to it, are questions for a lawyer or the film supplier, so we do not present PVC/PCTFE on this page as a ready option.

Tablets and capsules are sealed on an Uhlmann B 1240, which forms the cavities, fills them, seals the lidding foil and cuts out each blister in one pass, and are then packed into printed cartons on an IMA IC 150. The Uhlmann B 1240 is built to run PVC, PVC/PVDC, PVC/PCTFE and cold-formed aluminium. That list shows what the machine is built for; it is not a statement of which films the plant holds.

The carton can be part of the pack too. WHO's guideline for medicines lets the secondary pack count as part of the container closure system in a stability study if it has protective properties and the labelling clearly tells the user to store the product in both the primary and the secondary pack, as in "store tablets in blisters in the provided cartons".

What does WHO say about aluminium blisters?

WHO's stability guideline lists aluminium/aluminium blisters for solid dosage forms among its examples of impermeable containers, meaning containers that give a permanent barrier to the passage of gases or solvents. For products in such containers, the same guideline allows stability studies at any controlled or ambient humidity.

Three limits come with it. The guideline is written for medicines, so a supplement regulator or an importer may still ask for data at its own condition. Aluminium is opaque, so the dose cannot be seen through the cavity. And cold-formed cavities are shallower than thermoformed ones: on the B 1240, forming depth is up to 24 mm for PVC (thermoforming), while cold-formed aluminium is shallower, which limits the size of dose a cavity can take.

When does a bottle with desiccant keep a product longer?

In at least one published case: a 2017 modelling study estimated a longer shelf life for one tablet in a bottle with desiccant than in an aluminium blister. Published in the trade journal Pharmaceutical Technology, it looked at one moisture-sensitive multivitamin tablet, containing 100 mg of thiamine, at 30 °C/75 % RH in four pack types, with the bottles modelled at 60 cc holding 30 tablets.

The authors concluded that, for that tablet, the longest shelf life would not come from the impermeable aluminium blister. Read it with its limits: it is a calculation for one product at one condition, not a test; it appeared in a trade journal; and its figure is credited to a desiccant supplier. It is one worked case rather than a rule.

A blister is therefore not always the stronger pack. Which pack holds a product longer depends on the formula, the film and the pack size.

What do regulators in hot markets ask about the pack?

Each asks something different: of three documents we have read, Ghana's asks for stability data under WHO zone IVb conditions in the pack the product will be marketed in, Saudi Arabia's asks for a document on the packaging material of heat- or humidity-sensitive tablets and capsules, and Egypt's places the country in zone IVa.

This is a reading of published documents, not legal advice and not a promise of registration. Registering the product in the country of sale is the brand owner's step, taken by the brand owner or a local applicant as each country requires. From us come the Certificate of Analysis and the specification with each batch, and copies of the plant's certificates on request.

For tablets and capsules, the same SFDA food guide also lists a Pharmaceutical GMP Certificate among the documents it asks for. The plant's GMP certification is for food supplements, under the Food Supplements Europe guide, not pharmaceutical GMP. Whether and how a registration file can meet that SFDA requirement is a question for your importer to settle.

The manufacturing group behind the plant already supplies many clients in Africa, and its main markets are the United Arab Emirates, Saudi Arabia and Lebanon.

What should I send with an enquiry for a hot market?

The product, the market where it will be sold, and anything your importer or regulator has already asked for.

Whatever the market, the same documents come with every order. Each batch ships with a Certificate of Analysis and its product specification. The plant is ISO 22000, GMP and HACCP certified and FDA registered; copies of the certificates with their numbers are sent to clients on request.

What your product decides

The format and size of the dose, how readily it takes up moisture, the market and the way it travels each change something about the pack. Each has its cost in time, run or risk.

Questions buyers ask about hot and humid markets

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Climatic zones by country · Shelf life and storage · Manufacturing · Quality and certificates