A recent study published in the Indian Journal of Medical Research shows that in comparison to calendula, bentonite has better healing powers and is more effective in treating infantile diaper dermatitis. 
Infantile diaper dermatitis (DD) is an acute inflammatory reaction produced in the skin around the diaper as a result of frequent or prolonged contact with urine, stool or moisture. It may be exacerbated by Candida infection and abrasion. Physical appearance may be in the form of erythema, flakes, papules, or lesions in areas like buttocks, thighs, scrotum and mons pubis.
Bentonite is a mineral form of aluminum phyllosailicate. Formal or mineral soap are the other names of Bentonite in pharmacy. It is used as a moisturizer, skin protector and water absorbent. Earlier studies show that Calendula may be effective in non-complicated cases. 
A study was undertaken in Iran to compare the effect of topical application of bentonite and calendula creams in treating infantile diaper dermatitis. It was a double blind randomized control trial in which 100 infants with DD were selected randomly amongst the patients referred to the outpatient pediatric clinics of Imam Khomeini hospital and a healthcare center in Khomein city, Iran. They were divided into two groups of 50 each for test and control studies.
Equal quantities of the two ointments were taken and the contents were validated by 10 faculty members in Kashan and Arak Universities of Medical Sciences.
The affected area was observed on the first visit. Training was given to the mothers about how to apply the cream and then after treatment the affected area was observed again after three days.
The mean age of infants treated with Bentonite was 7.35±6.28 months and for those treated with Calendula was 6.45±5.53 months. In the first six hours overall 88% of diaper rashes in the infants treated with Bentonite started showing improvement while the rate of improvement in infants treated with Calendula was 54%. Infants treated with Bentonite were cured completely in the first three days as compared to 52 per cent of infants treated with Calendula. The mean times of recovery in Bentonite group were 44.14±23.95 and in Calendula group it was 86.34±24.13 hours.
The estimated result showed that Bentonite had faster healing effect than Calendula and improved infantile diaper dermatitis more effectively. Though neither of the groups showed any side effects, the results may not be completely reliable as the study sample was small and the study was conducted on the infants having mild to moderate DD. Further multicenter studies are needed to verify these interpretations on a larger sample.
1. Mansoreh Mahmoudi, Mohsen Adib-Hajbaghery, Mahdi Mashaiekhi. Comparing the effects of Bentonite & Calendula on the improvement of infantile diaper dermatitis: A randomized controlled trial. Indian Journal of Medical Research; 2015; 142:742-746.
2. Panahi Y, Sharif MR, Sharif A, Beiraghdar F, Zahiri Z, Amirchoopani G, et al. A randomized comparative trial on the therapeutic efficacy of topical Aloe vera and Calendula officinalis on diaper dermatitis in children. Scientific World Journal 2012; 2012 : 810234.