Bad breath is caused by the bacteria present in the mouth. So as not to cause problems for himself or for others, the Prophet ﷺ used the siwak, which is available commercially in the form of toothpaste or cream, but which is also used as is.
Indeed, the siwak has an antibacterial and anti-inflammatory component. It's also important to drink plenty of water, since a lack of water encourages the growth of bacteria in the mouth. In addition, fennel and mint help fight bad breath. What's more, to combat the bacteria responsible for bad breath, we need "good" bacteria such as acidophilus, which is found in yogurt but is also available in capsules; and to maintain a healthy gut flora, two capsules a day can be taken. Finally, to boost the immune system and maintain healthy gut flora, there is spirulina.
What the science says: teeth and gums, probiotics and the microbiome
Here is what published research says about the remedies mentioned above, for context — these studies address material causes; healing belongs to Allah.
Teeth and gums
Siwak reduces plaque and gum inflammation (Saudi Med J, 2015) (J Ethnopharmacol, 2022); propolis is being studied for oral health (J Funct Biomater, 2024), and honey for mouth sores. Salt water mouth rinses, clove for tooth pain, less sugar: the basics. Precaution: a cavity, an abscess, or a gum that keeps bleeding needs a dentist's care — natural remedies can bring relief in the meantime, but they don't repair the underlying problem.
Probiotics and the microbiome
The gut, the "second brain" as the professor calls it, hosts a microbiome whose balance shapes overall health. Probiotics improve symptoms of irritable bowel syndrome according to a meta-analysis in Gastroenterology (Gastroenterology, 2023) (Front Cell Infect Microbiol, 2022), and microbiome imbalance is linked to numerous diseases (Int J Mol Med, 2021). Precaution: choose strains that have been studied and suited to the condition; naturally fermented foods (yogurt, kefir, lacto-fermented vegetables) are a simple everyday source.
