July 21, 2026, 7:35 am | Read time: 2 minutes

Silicone sealants are intended to protect bathrooms and sanitary areas from moisture damage and mold. They often do, as a practical test by the magazine “Ökotest” (Issue 5/2023) has shown. However, “their practical advantages are based on a number of problematic substances,” the testers write. “Ökotest” took a closer look at 20 sealants.

Sealants in “Ökotest”–problematic substances found

First and foremost, “Ökotest” mentions organotin compounds in sealants: They help silicone cure after application. However, the commissioned labs found such high levels in ten of the products that they only received a “poor” rating overall.

The compounds mainly include dioctyltin (DOT) and dibutyltin (DBT). They are suspected of harming the immune system and the fetus. The toxic tributyltin (TBT) was also found in elevated levels and is hardly degradable in the environment.

Related: How to apply clean silicone joints in 8 steps

Almost all products in the test also contain isothiazolinones, which are intended to act as a biocide against mold but can trigger allergies. This also applies to dichloroctylisothiazolinone (DCOIT), found in seven test candidates. Ten sealants also release a considerable amount of volatile organic compounds (VOC) during application. VOCs can cause headaches and dizziness, which is why “Ökotest” advises ventilating rooms when using the sealants.

Only one sealant scores “very good”

Of the 20 silicone sealants–priced between 4.06 euros and 17.22 euros per 300 milliliters–three were rated “satisfactory,” and three “sufficient.” Three were rated “good”–the products “Akkit 601 Sanitär Silikon, white” (7.64 euros), “OBI Sanitär-Silikon, white” (7.73 euros), and “Toom Sanitär Silikon, white” (8.51 euros). The test winner with the only “very good” rating is “Probau Sanitär-Silikon eco, white” (7.69 euros).

with material from dpa