Interferon is a protein released by the cells of the body when they are under attack from a virus or other invader. When interferon is released, it sets off a series of reactions in nearby cells to help them defend against the infection.
Interferon is, therefore, a critical part of the immune system.
There are three basic forms of interferon. These are alpha and beta, also known as type 1, while gamma is known as type 2. Each form of interferon has different effects on the body.
As well as occurring naturally in the body, interferon is also used as a treatment for various health disorders, including multiple sclerosis (MS), some types of cancer, and hepatitis C.
The side effects of interferon can be grouped into three categories, according to Cancer Research UK. These are as follows:
Common side effects

Common side effects are those that affect more than 10 percent of users. They include:
- dizziness
- pain, redness, or swelling at the point of injection
- loss or thinning of hair
- reduced appetite and weight loss
- breathlessness and pale skin
- being more likely to bruise and bleed
- being more likely to pick up an infection
- exhaustion and weakness
- flu-like symptoms
- stomachache
- diarrhea
- nausea
- depression and anxiety
- insomnia
- sore throat
- headache
- cough
- joint and muscle pain
- skin rash
Occasional side effects
Occasional side effects affect between 1 and 10 percent of people. They include:
- drowsiness
- changes to the liver
- heart muscle damage
- allergic reactions
- loss of fertility, including possible early menopause
- periods stopping
- thirst and dry mouth
- raised blood pressure
- worsening migraines
- decreased sex drive
- swollen lymph glands
- indigestion
- constipation
- flushed skin
- breast pain
- vaginal dryness
- testicle pain
- a metallic taste to foods
- sore and reddened eyes
- blocked nose
- sleepwalking
- sweating more
- urinating more often
Rare side effects
Rare side effects affect less than 1 percent of people. They include:
- shakes
- pins and needles
Some side effects are more serious than others. Here is a look at some of the more severe side effects and what should be done about them.
Depression
One of the common and potentially most serious side effects of treatment with interferon is depression.
A
- poor sleep quality
- chronic inflammation in the body
- certain genetic factors
- a lack of social support from others
The review found that using antidepressants along with interferon might be helpful in staving off bouts of depression.
Unfortunately, depression caused by interferon use is likely to become a long-term, recurring condition, according to a
Infertility and early menopause
Infertility is an occasional side effect of interferon use and can affect either men or women.
Male infertility from interferon might be reversed after some months or years. However, female infertility will usually be a result of the drug triggering early menopause. As such, it will be permanent.
Anyone hoping to become a parent who is due to have interferon treatment should speak to their doctor about freezing their sperm or eggs before the procedure.
Heart damage
Some past research has found evidence that interferon might lead to heart damage.
One
At the same time, a
The connection between interferon and heart damage is not clearly understood, but it is worth being mindful of when someone is considering treatment.
Anyone who is concerned, especially those with a history of heart disease, should discuss this with their doctor before starting interferon treatment.
High blood pressure
A
The authors noted that this particular issue was rare and had not previously been reported. But it was, nonetheless, a possible side effect of interferon to keep in mind.
The study noted that the underlying risk factors and causes of this issue were unclear, but it occurred during a long course of interferon treatment.
Interferon is usually given by injection underneath the skin of the thigh or belly. The drug may also be given through a drip.
In a
Before undergoing interferon treatment, people should have a lengthy and in-depth conversation with their doctor about what to expect, regarding side effects and symptoms.
After starting treatment, the right time to get in touch with a doctor is whenever these side effects present a real problem to well-being or interfere with someone’s quality of life.
A doctor who knows about any side effects may be able to help address these with medication, adjust the treatment plan, or offer advice on counseling and other services.