Even though aloe vera can be useful in many ways when used internally, there are some 'unexpected' side effects of aloe vera juice. It can cause skin allergy, diabetes, constipation, dehydration, diarrhoea, lower blood sugar levels, electrolyte imbalance, irregular heartbeat, kidney failure and many more. It is suggested by doctors to use the appropriate amount of aloe vera when having some allergies or sicknesses.