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Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
During pregnancy, a woman is more likely to experience bleeding gums and nosebleeds caused by hormonal changes that increase blood flow to the mouth and nose.
Drug abusers experience the following scenario: The pleasure given by their drug (or drugs) of choice is so strong that it is difficult to eradicate even after years of staying away from the substances involved. Certain triggers may cause a drug abuser to relapse. Research shows that long-term drug abuse results in significant changes in brain function that persist long after an individual stops using drugs. It is most important to realize that the same is true of not just illegal substances but alcohol and tobacco as well.
In ancient Rome, many of the richer people in the population had lead-induced gout. The reason for this is unclear. Lead poisoning has also been linked to madness.
Throughout history, plants containing cardiac steroids have been used as heart drugs and as poisons (e.g., in arrows used in combat), emetics, and diuretics.
![Conjunctivitis, with the characteristic “pinkeye” appearance. A yellow crusty exudate is also common](https://biology-forums.com/gallery/47/medium_14755_14_10_12_6_36_55_93941824.jpeg)
![Prolapsed uterus. (a) A prolapse is the abnormal drop of the uterus into the vagina, representing th](https://biology-forums.com/gallery/47/medium_14755_26_10_12_5_31_31_9714603.jpeg)