Side effects of stool softener, or laxative, use include diarrhea, stomach pain and cramping, according to WebMD. Throat irritation is a side effect of liquid forms of stool softener medication. Rare side effects include rectal bleeding and allergic reactions.
Different types of stool softeners work in different ways and have varying side effects, states Mayo Clinic. Oral stool softeners, which add moisture to stool and make it easier to pass, interfere with nutrient and medication absorption. Oral stool softeners can also cause an electrolyte imbalance over time, which leads to weakness, abnormal heart rhythms, confusion and seizures. Surfak and Colace are examples of oral stool softeners.
Benefiber, Metamucil, Citrucel and other oral bulk formers can cause bloating, cramps or worsened constipation if not taken with a sufficient amount of water, as stated by Mayo Clinic. This type of stool softener works by absorbing water to create soft, bulky stool.
Oral osmotics are another type of stool softener that can cause nausea, gas, cramping, bloating or excessive thirst, according to Mayo Clinic. This type of stool softener works by taking water from the colon and other body tissues to soften stool. Examples of this type of stool softener are MiraLAX and milk of magnesia.