The products will be polluted by germs if they contact with air outside so more preservatives are required. Customers have the right to know the service life. The operating life is useless for airless packaging but it is a legal requirement.

In terms of characteristics of materials, in addition to the research of physics and microorganism, the consistency of container materials and filling is supposed to be paid attention. Before using container materials, the stability of all sorts of materials needs to be measured for a long time. Take an airless dispenser whose insides are several kinds of plastic, flexible sealing gaskets and probably a spring made of blank, zinc-coated or laminated steel as an example, choosing different types of materials causes some potential problems.

Firstly, plastics. If the products are essential oils, they may permeate into or even dissolve plastics due to particular chemical substances. Polypropylene, one of the most resistant plastic materials, is more reliable. If you are still worried, glass or ceramics are better choices. Besides, synthetic materials absorbing short-chained esters to enhance plastification can absorb short-chained amphiphilic preservatives resulted in decrease concentration of preservatives. As a result, as time goes by, the microorganisms are more unstable. In terms of double wall jars, hard outer jars made from styrene-acrylonitrile is more suitable for decoration (surface, imprint) while softer polypropylene inner jars can make products more stable. In addition, releasing the substances into filling materials can make plastic fragile. There will be crevices if plastic containers (even double wall jars) contain water-free products. Moreover, despite recycled plastics are popular, they may be polluted by some substances which will diffuse in to filling materials and lead to skin reaction when using. The constituents of products are shown on recycled products but some chemicals may not be shown. Furthermore, remember that plastic may get dusty owing to electrostatic charge.

Secondly, elastomers (sealing gaskets). According to different materials and filling materials, sealing gaskets can soak or shrink so compatibility needs to be checked, especially when there are molecular organic substances. What should be noticed is that some people are allergic to natural rubber.

Thirdly, glass. Sodium ions can be released into aqueous media by cheap soda lime glass and the PH level can be improved on the basis of the buffering capacity of filling materials. Glass and ceramics which are not penetrative for gases, such as oxygen and water vapour, are better than synthetic materials which have permeability. For oxygen-sensitive products, they are supposed to be filled under protective gas atmosphere and then packed in glass containers. Additionally, protruding glass knobs are required for pipette containers with rubber seals.

Fourthly, metal. Steal springs in airless dispensers will be decomposed due to the warm and damp atmosphere though they do not contact with the filling. There will be chemical reaction between metal and acidic components of filling materials resulted from non-resistant or damaged internal coating. And complexing agents may cause soluble aluminium compounds.

Fifthly, airless dispensers. There are two types of airless dispensers. The first type is that the dispenser has double bottom part during filling so after filling the top section of the dispenser is attached and snapped in. Because the vacuum is generated by the dispenser top, the interior double bottom will be traced upwards. There is a tiny opening in the dispenser bottom so the air can fill in if the interior part moves upwards, which is special. In terms of the second type, the dispenser top is linked to bottom and the bottom can be opened at the back. The bottom equipped with an even bottom panel is filled from the rear side with a sliding disk. An opening in the sliding disk will be sealed tightly with a plastic nipple after superfluous air escaped by the opening. If we remove the bottom panel, we can see the upward movement of the sliding disk.

At present, new technologies are introduced ranging from internal mechanical system to the design of dispenser parts. For instance, the top of dispensers can be designed as a plate with a central opening to distribute products so that when pressing the plate, we do not need to touch the material and can squeeze products onto a fleece. This kind of design can be applied to preservatives free products.

Different types of cosmetic packaging have their own advantages and disadvantages so we should think twice before using them to select the most appropriate one.