Itching, medically known as pruritus, is a common and often vexing sensation that compels us to scratch. While many instances of itching are easily attributed to surface-level irritations like dry skin, insect bites, or rashes, some individuals experience a persistent, deep itch that feels as though it is occurring "under the skin." This type of itching, often described as a crawling or tingling sensation, can be particularly distressing as scratching the surface provides little to no relief. Understanding the potential causes of this "under the skin" itch is crucial for effective diagnosis and management.

---

Key Insights into Itching Beneath the Skin

• Neuropathic Itch: Often originating from nerve damage rather than a skin issue, this type of itch can feel like it's deep within the tissues.
• Systemic Conditions: Diseases affecting internal organs like the liver, kidneys, or thyroid can manifest as generalized itching, sometimes perceived as being beneath the skin.
• Underlying Illnesses: While less common, certain blood disorders and even some cancers can cause itching that may be felt internally.

---

The Complex Nature of Itch

The sensation of itching is a complex neurological process involving specific nerve fibers in the skin that transmit signals to the brain. These nerve fibers are distinct from those that sense pain or touch. While histamine is a well-known mediator of itch, other chemical mediators and mechanisms can also play a role, explaining why antihistamines are not always effective in relieving itching.

Itching can be classified into several categories based on its origin:

Cutaneous or Pruritoceptive Itch

This is the most common type of itch, arising from the skin itself due to inflammation or irritation. Examples include itching from dry skin, eczema, hives, or insect bites.

Neuropathic Itch

This type of itch results from damage or dysfunction of the nervous system, either in the peripheral nerves (those outside the brain and spinal cord) or the central nervous system (brain and spinal cord). The itch sensation originates from the damaged nerves themselves, rather than from a stimulus on the skin surface. This is frequently described as feeling "under the skin."

Neurogenic Itch

This itch originates in the central nervous system but is triggered by mediators that do not directly involve nerve damage. It is often associated with systemic diseases.

Psychogenic Itch

This type of itch is associated with psychological factors, such as stress, anxiety, or depression.

---

Delving into the Causes of "Under the Skin" Itch

When itching is perceived as being "under the skin," it often points towards causes that are not simply surface-level skin irritations. These can range from nerve issues to underlying systemic diseases.

One of the primary culprits for a deep, non-relievable itch is neuropathic itch. This occurs when there is damage or irritation to the nerves that transmit itch signals. This damage can occur at various points along the nerve pathway, from the nerve endings in the skin to the spinal cord and brain.

Conditions Leading to Neuropathic Itch

Several conditions can cause neuropathic itch, including:

• Shingles (Herpes Zoster): After the rash of shingles clears, some individuals experience persistent nerve pain and itching in the affected area due to nerve damage. This is known as post-herpetic neuralgia.
• Diabetes: High blood sugar levels in individuals with diabetes can lead to nerve damage (diabetic neuropathy), which can manifest as burning, tingling, numbness, and sometimes itching, often in the extremities.
• Multiple Sclerosis: This neurological disorder, which affects the central nervous system, can cause various sensory symptoms, including itching.
• Pinched Nerves: Compression or pinching of nerves, such as in the spine, can lead to localized itching in the area supplied by that nerve.
• Stroke: Damage to the brain from a stroke can sometimes result in sensory changes, including chronic itching, often on one side of the body.
• Brachioradial Pruritus: This is a specific type of neuropathic itch that affects the forearms, often linked to nerve compression in the neck and sun exposure.

Unlike superficial itching, neuropathic itch may not respond well to typical anti-itch creams or antihistamines because the issue lies within the nervous system itself.

Another significant category of causes for itching, including that which feels "under the skin," are systemic diseases. These are conditions that affect internal organs and can have widespread effects on the body, including the skin.

Systemic Diseases Associated with Pruritus

Examples of systemic conditions that can cause itching include:

• Liver Disease: Liver conditions, particularly those causing cholestasis (reduced bile flow), can lead to a buildup of substances in the blood that trigger itching. This itching is often generalized and can be quite severe.
• Kidney Disease (Chronic Renal Failure): Kidney dysfunction can lead to an accumulation of waste products in the body, which can cause intense, generalized itching.
• Thyroid Problems: Both an overactive thyroid (hyperthyroidism) and an underactive thyroid (hypothyroidism) can be associated with itchy skin.
• Blood Disorders: Conditions like iron deficiency anemia or polycythemia vera (an increase in red blood cells) can sometimes cause itching.
• Certain Cancers: While less common, some cancers, such as lymphomas and leukemias, can present with itching as a symptom.
• Diabetes: As mentioned earlier, diabetes can cause itching through both neuropathic mechanisms and possibly other systemic effects.

In these cases, the itching is a symptom of the underlying disease, and effectively treating the systemic condition is key to relieving the itch.

Medications

Certain medications can also cause itching as a side effect. This can occur as an allergic reaction or as a non-allergic response. If you suspect a medication is causing your itch, it is important to consult with your doctor.

Psychogenic Factors

In some instances, psychological factors like stress, anxiety, or depression can contribute to or exacerbate itching. This is sometimes referred to as psychogenic itch or functional itch disorder. While the itch may not have a primary physical cause, the sensation is real and can be debilitating.

Chronic Pruritus of Unknown Origin (CPUO)

In some cases, despite a thorough medical evaluation, no clear cause for chronic itching can be identified. This is referred to as Chronic Pruritus of Unknown Origin. This can be a frustrating diagnosis, but treatments may still be available to help manage the symptoms.

---

Distinguishing Features: Itch With and Without a Rash

Itchy skin often occurs alongside a visible rash, which can provide clues about the underlying cause (e.g., eczema, hives, contact dermatitis). However, itching that is felt "under the skin" or generalized itching throughout the body may occur without any visible skin changes. This absence of a rash can sometimes point towards systemic or neuropathic causes rather than primary skin conditions.

Here is a table summarizing some potential causes of itching, distinguishing between those typically presenting with and without a rash:

Causes Often Presenting with a Rash	Causes Often Presenting Without a Rash
Eczema (Dermatitis)	Dry Skin (Xerosis)
Psoriasis	Nerve Disorders (Neuropathic Itch)
Hives (Urticaria)	Kidney Disease
Allergic Reactions (Contact Dermatitis)	Liver Disease
Insect Bites/Stings	Thyroid Problems
Scabies	Certain Cancers
Fungal Infections (Ringworm, Thrush)	Medication Side Effects
Heat Rash (Prickly Heat)	Iron Deficiency Anemia

---

Diagnosis and Seeking Medical Help

Given the diverse range of potential causes for itching, particularly when it feels like it's "under the skin" or is chronic, it is essential to consult a healthcare professional for a proper diagnosis. A dermatologist or a primary care physician can help determine the underlying cause through a physical examination, medical history, and potentially further tests.

The Diagnostic Process

The doctor will likely ask about the characteristics of your itch, such as:

• When did it start?
• Where on your body do you feel it?
• What makes it better or worse?
• Are there any other symptoms you are experiencing?
• What medications are you currently taking?
• Do you have any known medical conditions?

Based on this information, the doctor may perform a physical examination, looking for any skin changes. If no rash is present, or if a systemic cause is suspected, further investigations may be necessary, such as blood tests to check kidney function, liver function, thyroid levels, or blood cell counts. In some cases of localized itching without a clear cause, imaging studies or neurological evaluations may be considered to assess for nerve compression or damage. A skin biopsy may also be performed in certain situations.

---

Treatment Approaches

The treatment for itching that feels "under the skin" depends heavily on the underlying cause. Treating the root cause is the most effective way to achieve long-term relief.

Treating Underlying Conditions

If the itching is due to a systemic disease, managing that condition is paramount. This could involve medications for kidney or liver disease, managing blood sugar levels in diabetes, or treating thyroid imbalances.

Addressing Neuropathic Itch

Neuropathic itch can be challenging to treat, as traditional anti-itch remedies are often ineffective. Treatments may include:

• Oral Medications: Certain medications typically used for nerve pain, such as some anti-seizure drugs and antidepressants, can be helpful in modulating nerve signals and reducing neuropathic itch.
• Topical Treatments: While not always effective, some topical agents like capsaicin cream or topical anesthetics may provide relief for localized neuropathic itch. Topical corticosteroids may be used if there is accompanying inflammation, although they are not the primary treatment for the nerve issue itself.
• Injections: In some cases, injections of local anesthetics or botulinum toxin (Botox) may be used to target affected nerves.
• Neurostimulation Techniques: Techniques that involve stimulating nerves with electrical impulses may be considered for persistent and severe neuropathic itch.

Managing Dry Skin

Even when a systemic or neuropathic cause is present, dry skin can exacerbate itching. Using generous amounts of moisturizer can help improve the skin barrier and reduce irritation.

Other Supportive Measures

Other strategies that may help manage itching include:

• Avoiding scratching, which can worsen the itch-scratch cycle and damage the skin. Keeping nails short can help minimize damage if scratching occurs.
• Wearing loose, comfortable clothing made from natural fibers.
• Taking cool baths or showers.
• Applying cool compresses to the itchy areas.
• Avoiding irritants such as harsh soaps, hot water, and fragranced products.
• Stress management techniques, such as mindfulness or cognitive behavioral therapy, can be beneficial, especially if psychological factors are contributing to the itch.

---

Frequently Asked Questions

Why does it feel like the itch is under my skin?

When itching is felt "under the skin," it often suggests that the sensation is originating from the nerves themselves rather than from a superficial skin irritation. This can be due to nerve damage (neuropathic itch) or related to underlying systemic conditions that affect nerve signaling.

Can stress cause itching under the skin?

While stress doesn't directly cause nerve damage or systemic disease, it can contribute to or worsen the sensation of itching, including psychogenic itch which can feel deep-seated. Stress can also exacerbate existing skin conditions that cause itching.

When should I be concerned about itching under the skin?

You should consult a doctor if you experience chronic itching (lasting for more than six weeks), severe itching that disrupts your sleep or daily life, or itching that is accompanied by other symptoms such as fatigue, weight loss, changes in bowel habits, or jaundice (yellowing of the skin and eyes). Itching without a rash, especially when generalized, also warrants medical evaluation to rule out underlying systemic causes.

Can diet affect itching under the skin?

While diet can sometimes trigger allergic reactions that cause itchy rashes, its direct link to itching felt "under the skin" is less clear, unless the diet impacts an underlying systemic condition like kidney or liver disease.

Is scratching helpful for itching under the skin?

Scratching typically provides little relief for itching that originates from nerve issues or systemic conditions. In fact, excessive scratching can damage the skin, leading to infections and further complications.

---

References

• Itching | Pruritus | Itchy skin - MedlinePlus
• Itchy skin (pruritus) - Symptoms and causes - Mayo Clinic
• Pruritus: Causes & Treatments for Itchy Skin - Cleveland Clinic
• Causes of itchy skin | NHS inform
• Itchy skin without a rash: Possible causes and treatments
• 10 reasons your skin itches uncontrollably and how to get relief
• Itchy skin - NHS
• Neuropathic Itch: Causes and How to Get Relief - Verywell Health
• What is Neuropathic Itch? | ColumbiaDoctors
• Practical guide for the diagnosis and treatment of localized and generalized cutaneous pruritus (chronic itch with no underlying pruritic dermatosis) - PMC
• Pruritus: An Updated Look at an Old Problem - PMC
• Itching - Dermatologic Disorders - Merck Manual Professional Edition