One reason that herbs and spices are so popular as alternative medical therapies is that they are not only relatively non-toxic, but they are also healthful. Many herbs contain anti-oxidants, and some - such as turmeric - have been reported to provide protection against cancer.
Asafoetida and other common cooking herbs and condiments have never been shown to cause serious health problems other than gastrointestinal upset. However, it is possible that any beneficial agent if taken in excessive doses for a prolonged time could be harmful. In contrast normal doses of spices make life more pleasurable and are medically useful for digestion and normal health maintenance.