Why Do You Have A Hemorrhoid? Science Explained

Hemorrhoids are not something you catch. They are part of your normal anatomy. Everyone has them. The question is why they sometimes swell, bleed, or hurt. The answer comes down to pressure, tissue structure, and what happens when the cushions of blood vessels inside your anal canal get pushed past what they can handle.

Your anal canal contains three soft pads of vascular tissue — sometimes called anal cushions — that help maintain continence. They sit just inside the anal opening and fill with blood to help seal the canal. When those cushions become enlarged, inflamed, or displaced, they become what we call hemorrhoids. The medical term for the condition is hemorrhoidal disease.

This article explains the anatomy, the mechanics of why these cushions swell, what makes some people more prone to it, and what the evidence actually shows about treatment and prevention.

What Are Hemorrhoids and Why Does Everyone Have Them?

Hemorrhoids are normal anatomical structures, not abnormal growths. They are vascular cushions made of blood vessels, connective tissue, and smooth muscle that sit in the anal canal. They contribute to fine control of bowel movements. Without them, the anal canal would not close as effectively.

The cushions are located in three typical positions — left lateral, right anterior, and right posterior — in most people. They are not a design flaw. They are part of how the body maintains continence.

The trouble starts when these cushions become engorged or slide downward. That is when they cross from normal anatomy into a medical problem. The term “hemorrhoid” is often used to describe both the normal structure and the symptomatic condition, which causes confusion.

There are two types based on location. Internal hemorrhoids sit above the dentate line — a boundary inside the anal canal that separates tissue with pain sensation from tissue without it. External hemorrhoids sit below that line, where nerve endings are plentiful. This anatomical difference explains why external hemorrhoids tend to hurt more while internal ones often bleed without pain.

Why Do You Have A Hemorrhoid? The Mechanics Behind It

The core mechanism is increased pressure in the veins and tissues of the anal canal. When pressure rises repeatedly or stays elevated, the vascular cushions stretch, engorge, and eventually slide downward. This is similar to what happens to varicose veins in the legs, though the anatomy is different.

Several things can drive that pressure:

• Straining during bowel movements — pushing hard increases intra-abdominal pressure, which pushes blood into the anal cushions and weakens the supporting tissue over time.
• Chronic constipation — hard stools require more pushing and sit longer in the rectum, increasing pressure.
• Prolonged sitting on the toilet — gravity and positioning increase pressure on the anal cushions. The longer you sit, the more the tissue engorges.
• Pregnancy — the growing uterus presses on pelvic veins, and hormonal changes relax connective tissue. Hemorrhoids are common during pregnancy and after childbirth.
• Obesity — excess body weight increases intra-abdominal pressure, which can affect the pelvic veins.
• Low-fiber diet — fiber keeps stool soft and bulky. Without it, stools are harder and require more effort to pass.
• Aging — the connective tissue that supports the anal cushions weakens over time. This is one reason hemorrhoids become more common with age.

It is worth noting that many people with these risk factors never develop symptomatic hemorrhoids, and some people with none of them do. The relationship between pressure and symptoms is not perfectly predictable. Genetics may play a role in tissue strength, though this is not fully understood.

What Are the Symptoms of Internal vs. External Hemorrhoids?

The symptoms depend on where the hemorrhoid is and whether it has thrombosed — meaning a blood clot has formed inside it.

Internal hemorrhoids typically cause painless bleeding. You might see bright red blood on toilet paper or in the bowl after a bowel movement. Because the tissue above the dentate line lacks pain nerve endings, these hemorrhoids often do not hurt unless they prolapse — meaning they push out through the anal opening.

Internal hemorrhoids are graded by how far they prolapse:

• Grade I — No prolapse. The cushion is enlarged but stays inside.
• Grade II — Prolapse during a bowel movement but return on their own.
• Grade III — Prolapse and require manual pushing back in.
• Grade IV — Permanently prolapsed and cannot be pushed back in.

External hemorrhoids are covered by skin with pain fibers. They can cause itching, discomfort, swelling, and a palpable lump near the anal opening. When a blood clot forms inside one — called a thrombosed external hemorrhoid — the pain can be intense and sudden.

Both types can cause itching or irritation, often from mucus or small amounts of stool that get trapped around the swollen tissue.

What Conditions Can Look Like Hemorrhoids?

Not every lump or bleed near the anus is a hemorrhoid. Several other conditions can produce similar symptoms, and some are more serious.

Anal fissures are small tears in the lining of the anal canal. They cause sharp pain during bowel movements and often a small amount of bright red blood. They are commonly confused with hemorrhoids but are a different problem.

Anorectal abscesses are infections that cause a painful, swollen lump. They may come with fever and usually require medical treatment.

Anal fistulas are abnormal tunnels between the anal canal and the skin. They can drain pus or fluid.

Colorectal cancer can cause rectal bleeding. This is why any new rectal bleeding should be evaluated by a doctor, especially in people over 45 or those with a family history.

Inflammatory bowel disease — including Crohn’s disease and ulcerative colitis — can cause anal symptoms that mimic hemorrhoids.

Because these conditions can look alike, a physical exam is important. Do not assume bleeding is “just hemorrhoids” without a proper evaluation.

What Actually Helps: Evidence-Based Treatment Options

Most mild hemorrhoid symptoms improve with conservative measures. The evidence for these approaches is generally strong for symptom relief, though they do not necessarily shrink the hemorrhoid itself.

Fiber and fluids. Increasing dietary fiber softens stool and reduces straining. Fiber supplements like psyllium are commonly recommended. Research consistently shows that fiber improves symptoms and reduces bleeding in mild cases.

Sitz baths. Warm water soaks may relieve pain and itching. The evidence for this is not strong, but it is widely recommended and low-risk.

Topical treatments. Over-the-counter creams and suppositories may contain lidocaine for pain or hydrocortisone for inflammation. These can help with symptoms short-term but do not treat the underlying problem. Prolonged use of steroid creams can thin the skin.

Stool softeners. These can help if constipation is a factor. They are not a long-term solution.

Minimally invasive procedures. For persistent or higher-grade hemorrhoids, options include rubber band ligation, sclerotherapy, and infrared coagulation. Rubber band ligation is one of the most commonly performed office procedures and has good evidence for effectiveness in grade I-III internal hemorrhoids.

Surgery. Hemorrhoidectomy is reserved for severe or recurrent cases. It is effective but more painful and has a longer recovery than office procedures.

No single treatment works for everyone. The choice depends on the type, grade, and severity of symptoms, as well as patient preference.

Can You Prevent Hemorrhoids From Coming Back?

You cannot change your anatomy or reverse age-related tissue changes. But you can reduce the pressure that makes symptoms worse.

The most consistent evidence supports:

• Getting enough fiber — the USDA recommends about 25 grams per day for adult women and 38 grams for adult men, though most Americans fall short.
• Drinking enough water to keep stool soft.
• Not straining or sitting on the toilet for long periods.
• Staying physically active, which helps bowel regularity.
• Going when you feel the urge — delaying can lead to harder stools.

For people who are pregnant, hemorrhoids often improve after delivery as pressure on pelvic veins decreases and hormone levels return to baseline. However, some women continue to have symptoms postpartum.

If you have recurrent hemorrhoids despite these measures, talk to your doctor about whether an underlying condition — like chronic constipation or a structural issue — might be contributing.

When Should You See a Doctor?

Any new rectal bleeding should be evaluated. This is especially true if you are over 45, have a family history of colorectal cancer, or have other symptoms like weight loss, changes in bowel habits, or abdominal pain.

See a doctor promptly if you have:

• Severe pain, especially with a lump near the anus
• Bleeding that is heavy, dark, or mixed with stool
• Signs of infection — fever, pus, or increasing redness
• Symptoms that do not improve after a week of home care

Most hemorrhoids are not dangerous. But the symptoms can overlap with more serious conditions. Getting checked is not overreacting. It is the right call.