None whatsoever. The cards are specifically designed to detoxify, restore and enhance your body through your own life force energy (prana). If you find that your body is highly toxic and ill, this is why it's recommended to use one card per day and monitor yourself to see how you feel. A reminder that you only have to look at the card for at least 60 seconds and no longer. The same applies if you place the card on your body: a minimum of 60 seconds. If you charge you water with an AetherX Card, sip it very slowly. Each body can react differently depending on their level of toxicity. If the body feels like it is responding to intensely to the AetherX Cards, its recommended to put them aside for a few days as you work with transitional dietary and exercise routines. As your strength returns, you can go back to using the AetherX Cards. Remember to drink plenty of water and to get rest. This is why it's best to use a AetherX Card in the morning or latest, the midday when you first begin. Understand that no one person is identical to another. Everyone will feel the effects of the AetherX Cards in their own way, so please start very gentle with yourself and work your way up slowly with one card per day.