Final answer:
Disease and medication can stimulate the onset of the telogen stage and cause the production of abnormal, brittle hairs.
Step-by-step explanation:
Stimulation of the onset of the telogen stage or causing the production of abnormal, brittle hairs can be caused by disease and medication (SEO keyword: disease and medication). Certain diseases and medications can disrupt the normal hair growth cycle and lead to hair loss. Additionally, factors such as climate changes, well-balanced diet, and products and appliances may also affect the health and growth of hair but may not directly cause abnormal hairs or telogen stage onset.