Antihistamines are a group of pharmaceuticals that enter the environment and may affect microorganisms that regulate decomposing of organic matter and the release of carbon and nitrogen from soils. In this study I investigated if the antihistamine fexofenadine decreases the concentration of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) from humus. I used humus from two vegetation types (heath and meadow), and used a batch experiment approach, where humus was mixed with fexofenadine solutions (2000 ng/L and 20 000 ng/L). After ten days in room temperature, the samples with fexofenadine were compared with batches containing pure water solutions (control). I found differences in the concentration of DOC, DON and pH that were dependent on the studied vegetation types. There were higher concentrations of DOC and DON in heath (35.9 mg/L and 2.0 mg/L) than in the more nutrient rich meadow (9.2 mg/L and 0.5 mg/L). The latter vegetation type did also have a higher pH. In contrast to my hypothesis, the concentration of DOC and DON was not significantly affected by the fexofenadine. However, if considering a 90%-level of significance, there were a significant interaction effect where concentration of DOC decreased in meadow and increased it in heath. A possible vegetation specific effect of fexofenadin seems plausible as microbial biomass and activity in the vegetation types are known to differ. My findings cannot exclude that fexofenadine stimulates degradation of DOC in the more microbial active meadow humus, but not in the humus of heath where activities are lower.