Treatment depends substantially of the type of ICH. Rapid CT scan and other diagnostic measures are used to determine proper treatment, which may include both medication and surgery.

- Tracheal intubation is indicated in people with decreased level of consciousness or other risk of airway obstruction.

- IV fluids are given to maintain fluid balance, using isotonic rather than hypotonic fluids.

Surgery is required if the hematoma is greater than , if there is a structural vascular lesion or lobar hemorrhage in a young patient.

- A catheter may be passed into the brain vasculature to close off or dilate blood vessels, avoiding invasive surgical procedures.

- Aspiration by stereotactic surgery or endoscopic drainage may be used in basal ganglia hemorrhages, although successful reports are limited.

Intracranial hemorrhage is a serious medical emergency because the buildup of blood within the skull can lead to increases in intracranial pressure, which can crush delicate brain tissue or limit its blood supply. Severe increases in intracranial pressure (ICP) can cause brain herniation, in which parts of the brain are squeezed past structures in the skull.

Intracranial hemorrhage (ICH), also known as intracranial bleed, is bleeding within the skull. It includes intracerebral bleeds (intraventricular bleeds and intraparenchymal bleeds), subarachnoid bleeds, epidural bleeds, and subdural bleeds.

Intracerebral bleeding affects 2.5 per 10,000 people each year.

A number of specific recommendations have been made for women including taking aspirin after the 11th week of pregnancy if there is a history of previous chronic high blood pressure and taking blood pressure medications during pregnancy if the blood pressure is greater than 150 mmHg systolic or greater than 100 mmHg diastolic. In those who have previously had preeclampsia other risk factors should be treated more aggressively.

Aspirin reduces the overall risk of recurrence by 13% with greater benefit early on. Definitive therapy within the first few hours is aimed at removing the blockage by breaking the clot down (thrombolysis), or by removing it mechanically (thrombectomy). The philosophical premise underlying the importance of rapid stroke intervention was summed up as "Time is Brain!" in the early 1990s. Years later, that same idea, that rapid cerebral blood flow restoration results in fewer brain cells dying, has been proved and quantified.

Tight blood sugar control in the first few hours does not improve outcomes and may cause harm. High blood pressure is also not typically lowered as this has not been found to be helpful. Cerebrolysin, a mix of pig brain tissue used to treat acute ischemic stroke in many Asian and European countries, does not improve outcomes and may increase the risk of severe adverse events.

Current clinical research ranges from studies aimed at understanding the progression and pathology of PVL to developing protocols for the prevention of PVL development. Many studies examine the trends in outcomes of individuals with PVL: a recent study by Hamrick, et al., considered the role of cystic periventricular leukomalacia (a particularly severe form of PVL, involving development of cysts) in the developmental outcome of the infant.

Other ongoing clinical studies are aimed at the prevention and treatment of PVL: clinical trials testing neuroprotectants, prevention of premature births, and examining potential medications for the attenuation of white matter damage are all currently supported by NIH funding.

Preventing or delaying premature birth is considered the most important step in decreasing the risk of PVL. Common methods for preventing a premature birth include self-care techniques (dietary and lifestyle decisions), bed rest, and prescribed anti-contraction medications. Avoiding premature birth allows the fetus to develop further, strengthening the systems affected during the development of PVL.

An emphasis on prenatal health and regular medical examinations of the mother can also notably decrease the risk of PVL. Prompt diagnosis and treatment of maternal infection during gestation reduces the likelihood of large inflammatory responses. Additionally, treatment of infection with steroids (especially in the 24–34 weeks of gestation) have been indicated in decreasing the risk of PVL.

It has also been suggested that avoiding maternal cocaine usage and any maternal-fetal blood flow alterations can decrease the risk of PVL. Episodes of hypotension or decreased blood flow to the infant can cause white matter damage.

Lymphocystis is a common viral disease of freshwater and saltwater fish. The viruses that cause this disease belong to the genus Lymphocystivirus of the family Iridoviridae.

Aquarists often come across this virus when their fish are stressed such as when put into a new environment and the virus is able to grow.

The fish starts growing small white pin-prick like growths on their fins or skin and this is often mistaken for Ich/Ick (Ichthyophthirius multifiliis) in the early stages. It soon clumps together to form a cauliflower-like growth on the skin, mouth, fins, and occasional gills. Lesions at the base of the dorsal fin are common among freshwater species of Central American origin, most notably Herichthys carpentis & inside the mouth of Herichthys cyanoguttatus & Geophagus steindachneri. On the tail fin of Koi, Carps, & US native sunfish (Lepomis sp.) On the side flanks of Walleye, Sauger & Flounder. On random head and/or tail areas of common goldfish, and oranda variants. This virus appears to present itself as a lesion(s) at differing locations depending on the species of fish being attacked, often complicating initial diagnosis.

Lymphocystis does show some host-specificity, i.e., each strain (or species) of lymphocystis can infect only its primary host fish, or some additional closely related, fish.

There is no known cure for this virus, though a privately owned fish research & breeding facility near Gainesville, Florida USA has reportedly been able to suppress the virus into remission using the human antiviral "Acyclovir" at the rate of 200 mg per 10 US gallons for 2 days. Otherwise, some aquarists recommend surgery to remove the affected area if it is very serious, followed by an antibiotic bath treatment to prevent a secondary bacterial infection of the open wounds.

Eventually the growths inhibit the fish's ability to swim, breathe or eat, and secondary bacterial infections usually kills the fish.

Usually the best cure is to simply give the fish a stress free life, a weekly bacteria treatment and the virus will slowly subside and the fins will repair themselves. This can take many months. Like most viral infections, even in humans, the first outbreaks are the most serious, whilst the immune system "learns" how to suppress it, the outbreaks become less severe over time assuming the organism survives the initial outbreaks.

Several health authorities have issued related guidance documents, which need to be considered for drug development:

- ICH (International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use)

- M3(R2) "Guidance on Nonclinical Safety Studies for the Conduct of Human Clinical Trials and Marketing Authorization for Pharmaceuticals"

- S9 "Nonclinical Evaluation for Anticancer Pharmaceuticals"

- S10 "Photosafety Evaluation"

- EMA (European Medicines Agency)

- "Note for Guidance on Photosafety Testing" (revision on-hold)

- "Question & Answers on the Note for Guidance on Photosafety Testing"

- FDA (U.S. Food and Drug Administration)

- MHLW/PMDA (Japanese Ministry of Health, Labour and Welfare / Pharmaceuticals and Medical Devices Agency)

The capture, transportation and culture of bait fish can spread damaging organisms between ecosystems, endangering them. In 2007, several American states, including Michigan, enacted regulations designed to slow the spread of fish diseases, including viral hemorrhagic septicemia, by bait fish. Because of the risk of transmitting "Myxobolus cerebralis" (whirling disease), trout and salmon should not be used as bait. Anglers may increase the possibility of contamination by emptying bait buckets into fishing venues and collecting or using bait improperly. The transportation of fish from one location to another can break the law and cause the introduction of fish and parasites alien to the ecosystem.

A phototoxic substance is a chemical compound which becomes toxic when exposed to light.

- Some medicines: tetracycline antibiotics, sulfonamides, amiodarone, quinolones

- Many cold pressed citrus essential oils such as bergamot oil

- Some plant juices: parsley, lime, and Heracleum mantegazzianum

- Others: psoralen

Though not a health concern in thoroughly cooked fish, parasites are a concern when human consumers eat raw or lightly preserved fish such as sashimi, sushi, ceviche, and gravlax. The popularity of such raw fish dishes makes it important for consumers to be aware of this risk. Raw fish should be frozen to an internal temperature of −20 °C (−4 °F) for at least 7 days to kill parasites. It is important to be aware that home freezers may not be cold enough to kill parasites.

Traditionally, fish that live all or part of their lives in fresh water were considered unsuitable for sashimi due to the possibility of parasites (see Sashimi article). Parasitic infections from freshwater fish are a serious problem in some parts of the world, particularly Southeast Asia. Fish that spend part of their life cycle in salt water, like salmon, can also be a problem. A study in Seattle, Washington showed that 100% of wild salmon had roundworm larvae capable of infecting people. In the same study farm raised salmon did not have any roundworm larvae.

Parasite infection by raw fish is rare in the developed world (fewer than 40 cases per year in the U.S.), and involves mainly three kinds of parasites: Clonorchis sinensis (a trematode/fluke), Anisakis (a nematode/roundworm) and Diphyllobothrium (a cestode/tapeworm). Infection by the fish tapeworm "Diphyllobothrium latum" is seen in countries where people eat raw or undercooked fish, such as some countries in Asia, Eastern Europe, Scandinavia, Africa, and North and South America. Infection risk of anisakis is particularly higher in fishes which may live in a river such as salmon ("shake") in Salmonidae, mackerel ("saba"). Such parasite infections can generally be avoided by boiling, burning, preserving in salt or vinegar, or freezing overnight. Even Japanese people never eat raw salmon or ikura (salmon roe), and even if they seem raw, these foods are not raw but are frozen overnight to prevent infections from parasites, particularly anisakis.

Below are some life cycles of fish parasites that can infect humans:

Poena cullei (from Latin 'penalty of the sack') under Roman law was a type of death penalty imposed on a subject who had been found guilty of parricide. The punishment consisted of being sewn up in a leather sack, sometimes with an assortment of live animals, and then being thrown into water. The punishment may have varied widely in its frequency and precise form during the Roman period. For example, the earliest fully documented case is from ca. 100 BCE, although scholars think the punishment may have developed about a century earlier (earlier than that, murderers, including parricides, would be handed over to the aggrieved family for punishment, rather than punishment being enacted by Roman state officials). Inclusion of live animals in the sack is only documented from Early Imperial times, and at the beginning, only snakes are mentioned. At the time of Emperor Hadrian (2nd century CE), the most well known form of the punishment was documented, where a cock, a dog, a monkey and a viper were inserted in the sack. However, at the time of Hadrian "poena cullei" was made into an optional form of punishment for parricides (the alternate being thrown to the beasts in the arena). During the 3rd century CE up to the accession of Emperor Constantine, "poena cullei" fell out of use; Constantine revived it, now with only serpents to be added in the sack. Well over 200 years later, Emperor Justinian reinstituted the punishment with the four animals, and "poena cullei" remained the statutory penalty for parricides within Byzantine law for the next 400 years, when it was replaced with the punishment for parricides to be burnt alive instead.

"Poena cullei" gained a revival of sorts in late medieval and early modern Germany, with late cases of being drowned in a sack along with live animals being documented from Saxony in the first half of the 18th century.

The "Wenxian Tongkao", written by Chinese historian Ma Duanlin (1245-1322), and the "History of Song" describe how the Byzantine emperor Michael VII Parapinakēs Caesar ("Mie li sha ling kai sa" 滅力沙靈改撒) of "Fu lin" (拂菻, i.e. Byzantium) sent an embassy to China's Song dynasty, arriving in November 1081, during the reign of Emperor Shenzong of Song (r. 1067-1085). The "History of Song" described the tributary gifts given by the Byzantine embassy as well as the products made in Byzantium. It also described forms of punishment in Byzantine law, such as caning, as well as the capital punishment of being stuffed into a "feather bag" and thrown into the sea. This description seems to correspond with the Romano-Byzantine punishment of "poena cullei".