Allantoin Solubility and Cloudiness in Refrigerated Formulation
Question
Why does my formulation containing Allantoin become cloudy when stored in the refrigerator, and is it normal for it to be clear?
Answer
Allantoin has limitations in its solubility in water, especially at low temperatures. The solubility of Allantoin in water decreases as the temperature drops.
According to the product information, Allantoin can dissolve in water up to approximately 0.5% at 25°C, and its solubility decreases further at lower temperatures.
If the finished product is stored in a refrigerator at around 6-8°C, the solubility in water reduces to only about 0.2%.
Therefore, if your formulation contains Allantoin at a concentration higher than 0.2%, when stored in the refrigerator, the excess Allantoin that cannot dissolve at the low temperature will crystallize out, causing the formulation to become cloudy.
Normally, if Allantoin is mixed at a concentration that does not exceed its solubility limit at the storage temperature, the formulation should be clear.
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