Diarrhea

Diarrhea is a condition in which the hamster may have frequent watery, loose bowel movements. Diarrhea in a hamster can become serious and life threatening. Diarrhea can cause dehydration rapidly in small animals. This condition can be associated with bacteria, such as Salmonella, Campylobacter E.coli, and is commonly referred to as Wet Tail In many cases of diarrhea, replacing lost body fluid and salts (rehydration) is the only treatment that may be needed.

In the absence of disease other causes of Diarrhea or loose stools may be allergies to food intolerance, or diary produce
Food intolerance is seen when feeding your pet with food that has been processed for human consumption. All processed foods contain additives: These are salts, sugars, chemicals, colouring, and synthetic vitamins that a hamster’s digestive system is unable to cope with.

Diarrhea in a hamster can lead to severe dehydration, and can become life threatening if left untreated.
An oral re-hydration therapy should be induced: Giving just water alone in this case is not the best way to restore fluid levels, and electrolytes. Using water alone will complicate the situation even more, as water will further dilute the minerals, salts and sugars in the body (see dehydration) Pedialyte is an oral electrolyte maintenance solution: Electrolyte solutions contain Sodium and Potassium salts, theses are used to replenish the body's water and electrolyte levels after dehydration.

Diarrhea: loose, or soft stools in a hamster, can also be caused by feeding too much fruit, all fruit contains Fructose, this is a naturally occurring sugar found in fruit. Feeding hamsters to much fruit will cause loose stools, or diarrhea depending on how much is eaten. Vegetables, especially green leaf vegetables are another common cause of loose stools.

Care should be exercised when feeding any green food to young hamsters; Dandelion, Cabbages, and Lettuce act as a laxative and can soften stools (See toxic) avoid feeding theses particularly on acquiring a new baby hamster. Should any sign of loose stools become noticeable then stop feeding all vegetables and fruit till the hamsters tummy has settled.
Dry feces stuck on the fur around the tail of the hamster may indicate a problem with loose stools, and maybe nothing more serious than a mild tummy upset. This is possibly a dietary issue needing adjustments; you need to think about what you are feeding him. Take into consideration some of the above mentioned foods.