Dehydration: Given the low blood pressure (88/55 mmHg) and relatively normal pulse (70 bpm), dehydration is a common and likely cause. It can result from various factors such as inadequate fluid intake, excessive fluid loss (e.g., diarrhea, vomiting), or environmental factors.

Hypovolemic Shock: This condition occurs when there's not enough blood volume in the body, leading to inadequate blood flow and oxygen delivery to vital organs. It could be due to severe bleeding (internal or external), significant burns, or severe dehydration.
Cardiogenic Shock: Although less likely given the normal pulse rate, cardiogenic shock (where the heart suddenly can't pump enough blood to meet the body's needs) is a possibility, especially if there's a history of heart disease.
Anaphylactic Shock: An allergic reaction that can cause a drop in blood pressure, but it's usually accompanied by other symptoms like rash, itching, swelling, etc.

Septic Shock: A life-threatening condition that arises when the body's response to an infection becomes uncontrolled and causes widespread inflammation. Early recognition and treatment are crucial.
Adrenal Insufficiency (Addisonian Crisis): A rare but potentially life-threatening condition where the adrenal glands do not produce enough cortisol and aldosterone. It can cause hypotension, among other symptoms.
Pulmonary Embolism: Although more commonly associated with symptoms like chest pain and shortness of breath, a large pulmonary embolism can cause hypotension and would be catastrophic if missed.

Neurogenic Shock: Typically seen in the context of spinal cord injury, leading to loss of sympathetic tone and subsequent vasodilation and hypotension.
Endocrine Disorders: Other than adrenal insufficiency, conditions like hypothyroidism or certain pancreatic tumors can cause hypotension, though they are less common and might present with additional symptoms.
Medication Side Effects: Certain medications can cause hypotension as a side effect, especially when first started or at high doses. Examples include antihypertensives, certain antidepressants, and drugs used in anesthesia.