Material Safety Data Sheet (MSDS) for Sodium lauryl sulfate gives the following information:
Section 11: Toxicological Information WARNING: THE LC50 VALUES HEREUNDER ARE ESTIMATED ON THE BASIS OF A 4-HOUR EXPOSURE. Acute oral toxicity (LD50): 1288 mg/kg [Rat.]. Acute toxicity of the dust (LC50): >3900 mg/m 1 hours [Rat]. 3MUTAGENIC EFFECTS: Mutagenic for bacteria and/or yeast. May cause damage to the following organs: skin.Hazardous in case of skin contact (irritant), of ingestion, of inhalation. Slightly hazardous in case of skin contact (sensitizer).Special Remarks on Toxicity to Animals:Lowest Published Lethal Dose: LDL [Rabbit] - Route: Skin; Dose: 10000 mg/kgSpecial Remarks on Chronic Effects on Humans: May cause adverse reproductive effects based on animal test data. No human data found.Special Remarks on other Toxic Effects on Humans:Acute Potential Health Effects: Skin: Causes mild to moderate skin irritation. May cause allergic reaction (dermatitis) Eyes: Causes moderate eye irritation. Inhalation: Material is irritating to mucous membranes and upper respiratory tract. May cause allergic respiratory reaction. Ingestion: Causes gastrointestinal tract irritation with nausea, vomiting, hypermotility, diarrhea, and bloating. May also affect behavior (ataxia, somnolence), and cardiovascular system. Chronic Potential Health Effects: Skin: Prolonged or repeated skin contact may cause allergic dermatitis. Ingestion: Prolonged or repeated ingestion may affect the liver. Inhalation: Prolonged or repeated inhalation may cause allergic respiratory reaction (asthma).
(From: http://www.sciencelab.com/msds.php?msdsId=9925002)
It does make sense not to ingest detergents unnecessarily.
Further, there are several other components in washing up liquids that are likely to have additional undesirable effects on health.
To rinse or not to rinse? It’s your decision.