Almonds can go bad if they are not properly stored. Though the almond is technically a seed, it is used as a nut and has a high fat content. This fat content is what makes the almond turn rancid quickly.
Unshelled almonds have the longest shelf-life. Shells should be intact, mold-free and have a clean, nutty smell. Ideally, the best almonds to buy come in airtight containers in which they are not exposed to heat or humidity.
Once home, almonds need to be stored in a cool, dry place. It is better to store them in the refrigerator for the long term and better still to store them in the freezer.