The US FDA has assigned the pregnancy category B status to Benadryl, which means that it is considered safe to use, as there are no known side effects. However, your doctor will be the best person to judge whether or not you should take Benadryl while you are pregnant. He will also decide on the quantity of intake.
Human carcinogen -- Benzene: Benzene is a chemical deemed to be carcinogenic to humans. The carcinogenicity of the substance may be influenced by the nature (e.g. inhalation, ingestion, skin contact), duration and level of exposure. Benzene exposure is associated mainly with an increased risk of developing leukemia or lymphoma.
Benzene is a colorless or light-yellow liquid chemical at room temperature. It is used primarily as a solvent in the chemical and pharmaceutical industries, as a starting material and an intermediate in the synthesis of numerous chemicals, and in gasoline. Benzene is produced by both natural and man-made processes. It is a natural component of crude oil, which is the main source of benzene produced today. Other natural sources include gas emissions from volcanoes and forest fires. How are people exposed to benzene? People are exposed to benzene primarily by breathing air that contains the chemical. Workers in industries that produce or use benzene may be exposed to the highest levels of the chemical, although federal and state regulations have reduced these exposures in recent decades. Similarly, limits on the amount of benzene allowed in gasoline have contributed to reduced exposures.